Projection type display apparatus with means for supplying an air cooling stream to a gap between a light receiving surface of a prism and a third surface of a closed triangular prismatic housing

ABSTRACT

A projection type display apparatus includes: a reflective polarizing plate for each color light which transmits each of R light, G light and B light having a P polarized component subjected to color separation by a color separation optical system therethrough, allows each transmitted light to enter a corresponding reflective liquid crystal panel for each color light, and reflects image light of each color having an S polarized component which has been subjected to light modulation in accordance with an image signal of each corresponding color light by the reflective liquid crystal panel for each color light; a transmission type polarizing plate for each color light which removes an unnecessary polarized component from the image light of each color reflected by the reflective polarizing plate for each color light; a color combination optical system which subjects the image light of each color transmitted through the transmission type polarizing plate for each color light to color combination; and a projection lens, wherein the transmission type polarizing plate for each color light is air-cooled by air-cooling means when the transmission type polarizing plate for each color light faces each incidence surface of the color combination optical system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a projection type display apparatuswhich comprises unnecessary polarized light removing means for eachcolor light which removes an unnecessary polarized component withrespect to image light of each color emitted from a reflective spatiallight modulation element (a reflective liquid crystal panel) for eachcolor light corresponding to each of R light, G right and B light, andalso comprises air-cooling means for air-cooling the unnecessarypolarized light removing means for each color light.

2. Description of the Related Art

Although a projection type display apparatus which magnifies andprojects a color image has various kinds of structural conformationsdepending on arrangement relationships of optical constituent members,there are a transmission type which allows light to be transmittedthrough a spatial light modulation element (which will be referred to asa liquid crystal panel hereinafter) using a liquid crystal panel or thelike and a reflection type which reflects light. In both of these types,white light emitted from a light source is divided based on each colorinto three primary color lights, i.e., R light (red light), G light(green light) and B light (blue light) by a color separation opticalsystem, the three primary color lights are respectively led to liquidcrystal panels for the R, G and B lights, the respective image lights ofthe R light, the G light and the B light subjected to light modulationin accordance with respective image signals for the R, G and B lights inthe respective liquid crystal panels for the R, G and B lights aresubjected to color combination by a color combination optical system,and color-combined image light acquired by the color combination opticalsystem is magnified and projected onto a screen from a projection lens.

At this time, there has been proposed a projection type displayapparatus having a configuration in which, when a quantity of the lightswhich enter a polarizer and a liquid crystal panel is increased in orderto increase luminance of the projected color-combined image light in theprojection type display apparatus, the polarizer and the liquid crystalpanel generate heat, but the polarizer and the liquid crystal panel arecooled by supplying cooling air in substantially parallel withrespective surfaces of the polarizer and the liquid crystal panel,thereby projecting the color-combined image light with higher luminanceonto the screen (see, e.g., Japanese Patent Application Laid-open No.2000-194073).

FIG. 1 is a structural view showing a conventional projection typedisplay apparatus. FIG. 2 is a side view showing an arrangement ofcooling fans in the conventional projection type display apparatus. FIG.3 is a perspective view showing a state in which a polarizer and aliquid crystal panel are cooled in the conventional projection typedisplay apparatus.

A projection type display apparatus 200 according to the prior art shownin FIG. 1 is disclosed in the above-described Japanese PatentApplication Laid-open No. 2000-194073, and will be briefly describedherein with reference to documents.

As shown in FIG. 1, in the conventional projection type displayapparatus 200, a parallel light ray emitted from a non-polarized lightsource 202 provided in a casing 201 is turned to visible light by aUV/IR cut filter 203, and this visible light is transmitted through andreflected by a first color separation dichroic mirror 204. Further, onecolor light transmitted through the first color separation dichroicmirror 204 travels forward to reach a reflecting mirror 205, and isreflected by this reflecting mirror 205 to change its direction 90°, andenters a first liquid crystal panel assembly 210A.

On the other hand, two color lights reflected by the first colorseparation dichroic mirror 204 change their directions 90° here to reacha second color separation dichroic mirror 206, and are transmittedthrough and reflected by this second color separation dichroic mirror206. Furthermore, one color light reflected by the second dichroicmirror 206 of the two color lights changes its direction 90° to enter asecond liquid crystal panel assembly 210B, and the other color lighttransmitted through the second color separation dichroic mirror 206travels forward to enter a third liquid crystal panel assembly 210C.

Here, the first to third liquid crystal panel assemblies 210A to 210Ccorresponding to RGB are respectively constituted as a transmission typein which a condenser lens 211, a polarizer 212, a liquid crystal panel213 and a polarizer 214 are sequentially arranged.

Moreover, one color light transmitted through the first liquid crystalpanel assembly 210A is transmitted through a first color combinationdichroic mirror 207 to enter a second color combination dichroic mirror209 and, on the other hand, one color light transmitted through thesecond liquid crystal panel assembly 210B is reflected by the firstcolor combination dichroic mirror 207 to enter the second colorcombination dichroic mirror 209, and the other color light transmittedthrough the third liquid crystal panel assembly 210C is reflected by areflecting mirror 208 to enter the second color combination dichroicmirror 209. The three color lights are subjected to color combination bythis second color combination dichroic mirror 209, and color-combinedimage light is magnified and projected onto a non-illustrated screen.

At this time, as shown in FIG. 2, there is a description in which fans221A to 221C as cooling means are provided on an outer side surface ofthe casing 201 in accordance with the first to third liquid crystalpanel assemblies 210A to 210C (FIG. 1). Additionally, an air stream fromthe fan 221A (221B, 221C) is supplied in a direction indicated by anarrow X and a direction indicated by an arrow Y in substantiallyparallel with respective surfaces of the polarizer 212 and the liquidcrystal panel 213 in each of the first to third liquid crystal panels210A (210B, 210C) through a fan duct 222A (222B, 222C), effectivecooling can be thereby performed, and it is possible to obtain theprojection type display apparatus 200 capable of projecting thecolor-combined image light having higher luminance onto a screen.

Meanwhile, according to the conventional projection type displayapparatus 200, since each polarizer 212 and each liquid crystal panel213 in the first to third liquid crystal panel assemblies 210A to 210Ccorresponding to RGB are respectively cooled by using the three fans221A to 221C and the three fan ducts 22A to 222C, the three coolingmeans disadvantageously have a large-scaled structural conformation.

Additionally, the conventional projection type display apparatus 200 haseach liquid crystal panel 213 for each of the R, G and B lightsconstituted as a transmission type, but acquisition of a high resolutionwith respect to a projected image is difficult in case of thetransmission type. Thus, when a reflective liquid crystal panel isadopted in order to achieve the high resolution, even if the coolingmeans in the conventional projection type display apparatus 200 are usedas they are, the cooling means likewise have a large-scaled structuralconformation.

SUMMARY OF THE INVENTION

Therefore, there has been demanded a projection type display apparatuswhich can remove an unnecessary polarized component to achieve highluminance and high contrast when color-combined image light obtained byperforming color combination of image lights of respective colorsemitted from reflective spatial light modulation elements for respectivecolor lights is projected by a projection lens in the projection typedisplay apparatus to which the three reflective spatial light modulationelements (reflective liquid crystal panels) are applied in accordancewith R light, G light and B light, and there has been also demanded aprojection type display apparatus which can cool the inside of theapparatus with respect to heat generation due to lights from a lightsource with a simple configuration.

Further, as another problem, in the projection type display apparatususing the reflective spatial light modulation elements for respectivecolors, optical components or a projection lens are interposed betweenthe reflective spatial light modulation elements for the respectivecolor lights and a screen on which lights are projected by theprojection lens, but there is a phenomenon that unnecessary reflectedlights reflected from respective interfaces of these optical componentsor the projection lens are projected onto the screen so that contrast islowered, and its solution has been demanded.

In order to achieve the above object, according to a first aspect of thepresent invention, there is provided a projection type display apparatus(10) comprising: a reflective spatial light modulation element (33) foreach color light corresponding to each of R light, G light and B light;each color light illuminating means (11-21) for illuminating thereflective spatial light modulation element (33) for each color lightwith each of the R light, the G light and the B light; a reflectivepolarizing plate (32) for each color light which transmits a polarizedcomponent in one direction of each of the R light, the G light and the Blight from each color light illuminating means (11-21) therethrough, andreflects as image light of each color a polarized component in the otherdirection different from the polarized light in one direction obtainedby subjecting each of the transmitted R light, G light and B light tolight modulation in accordance with an image signal of each color lightby the reflective spatial light modulation element (33) for each colorlight; unnecessary polarized light removing means (34, (35), (37)) foreach color light for removing an unnecessary polarized component withrespect to the image light of each color from the reflective spatiallight modulation element (33) for each color light reflected by thereflective polarizing plate (32) for each color light to emit the imagelight of each color without the unnecessary polarized component; a colorcombination optical system (40) which subjects the image light of eachcolor emitted from the unnecessary polarized light removing means (34,(35), (37)) for each color light to color combination to emit the thuscombined light as color-combined image light; and a projection lens (42)which projects the color-combined image light, wherein the unnecessarypolarized light removing means (34, (35), (37)) for each color light isa polarizing plate (34, (37)) which absorbs unnecessary polarized lightor a polarizing plate (35) which reflects the unnecessary polarizedlight.

According to the first aspect of the present invention, in theprojection type display apparatus to which three reflective spatiallight modulation elements (reflective liquid crystal panels) are appliedin accordance with R light, G light and B light in particular, aplate-like reflective polarizing plate (a so-called “wire gridpolarizer”) as polarization splitting means is arranged in accordancewith each of the R light, the G light and the B light between each colorlight illuminating means for illuminating the reflective spatial lightmodulation element for each color light and a color combination opticalsystem, whereby each color light from each color light illuminatingmeans and image light from the reflective spatial light modulationelement for each color light are assuredly subjected to polarizationsplit by the reflective polarizing plate for each color light. Further,when unnecessary polarized light removing means for each color light isarranged between the reflective spatial light modulation element foreach color light and the color combination optical system in order toremove unnecessary polarized light with respect to the image light ofeach color emitted from the reflective spatial light modulation elementfor each color light, since a polarizing plate which absorbs theunnecessary polarized light or a polarizing plate which reflects theunnecessary polarized light is used as the unnecessary polarized lightremoving means for each color light, color-combined image light fromwhich the unnecessary polarized light has been removed can beexcellently projected onto a screen, and hence high luminance and highcontrast can be achieved, which contributes to an improvement in qualityand reliability of the projection type display apparatus.

Furthermore, in order to achieve the above object, according to a secondaspect of the present invention, there is provided a projection typedisplay apparatus (10) comprising: a reflective spatial light modulationelement (33) for each color light corresponding to each of R light, Glight and B light; each color light illuminating means (11-21) forilluminating the reflective spatial light modulation element (33) foreach color light with each of the R light, the G light and the B light;a reflective polarizing plate (32) for each color light which transmitsa polarized component in one direction of each of the R light, the Glight and the B light from each color light illuminating means (11-21)therethrough, and reflects as image light of each color a polarizedcomponent in the other direction different from the polarized light inone direction obtained by subjecting each of the transmitted R light, Glight and B light to light modulation in accordance with an image signalof each color light by the reflective spatial light modulation element(33) for each color light; unnecessary polarized light removing means(34, (35), (37)) for each color light for removing an unnecessarypolarized component with respect to the image light of each color fromthe reflective spatial light modulation element (33) for each colorlight reflected by the reflective polarizing plate (32) for each colorto emit the image light of each color without the unnecessary polarizedcomponent; a color combination optical system (40) which subjects theimage light of each color emitted from the unnecessary polarized lightremoving means (34, (35), (37)) for each color light to colorcombination to emit the thus combined light as color-combined imagelight; and a projection lens (42) which projects the color-combinedimage light, wherein the unnecessary polarized light removing means (34,(35), (37)) for each color light is a polarizing plate (34, (37)) whichabsorbs unnecessary polarized light with respect to the R light and theG light and, on the other hand, it is a polarizing plate (35) whichreflects the unnecessary polarized light with respect to the B light.

According to the second aspect of the present invention, in theprojection type display apparatus to which three reflective spatiallight modulation elements (reflective liquid crystal panels) are appliedin accordance with R light, G light and B light in particular, aplate-like reflective polarizing plate (a so-called “wire gridpolarizer”) as polarization splitting means is arranged in accordancewith each of the R light, the G light and the B light between each colorlight illuminating means for illuminating the reflective spatial lightmodulation element for each color light and a color combination opticalsystem, whereby each color light from each color light illuminatingmeans and image light from the reflective spatial light modulationelement for each color light are assuredly subjected to polarizationsplit by the reflective polarizing plate for each color light.Furthermore, when unnecessary polarized light removing means for eachcolor light is arranged between the reflective spatial light modulationelement for each color light and the color combination optical system inorder to remove unnecessary polarized light with respect to the imagelight of each color emitted from the reflective spatial light modulationelement for each color light, since a polarizing plate which absorbs theunnecessary polarized light with respect to the R light and the G lightand a polarizing plate which reflects the unnecessary polarized lightwith respect to the B light are used as the unnecessary polarized lightremoving means for each color, color-combined image light from which theunnecessary polarized light has been removed can be further excellentlyprojected onto a screen by a projection lens by substantially providingthe reflective polarizing plate for the B light with heat resistingproperties or light stability with respect to the B light whosewavelength is shorter than those of the R light and the G light, wherebyhigh luminance and high contrast can be achieved, which furthercontributes to an improvement in quality and reliability of theprojection type display apparatus.

According to a third aspect of the present invention, air-cooling means(26) which air-cools the unnecessary polarized light removing means (34,(35), (37)) for each color light is further provided in the first orsecond aspect of the present invention.

According to the third aspect of the present invention, since theunnecessary polarized light removing means for each color light whichgenerates heat due to light from a light source is air-cooled by theair-cooling means having a simple configuration, the unnecessarypolarized light removing means for each color light can be preventedfrom being deteriorated due to heat generation.

According to a fourth aspect of the present invention, in any one of thefirst, second and third aspects of the present invention, a triangularprismatic housing (31) for each color light is arranged in proximity tothe color combination optical system (40), the triangular prismatichousing (31) for each color light having: a first surface (31 a) whichhas an inclination angle of approximately 45° with respect to an opticalaxis of each color light from each color light illuminating means(11-21) and on which the reflective polarizing plate (32) for each colorlight is attached; a second surface (31 b) which is orthogonal to theoptical axis of each color light transmitted through the reflectivepolarizing plate (32) for each color light and on which the reflectivespatial light modulation element (33) for each color light is attached;a third surface (31 c) which is orthogonal to the optical axis of eachcolor light obtained by reflecting reflected light from the reflectivespatial light modulation element (33) for each color light by thereflective polarizing plate (32) for each color and on which theunnecessary polarized light removing means (34, (35)) for each colorlight is attached; and a lower surface (31 d) and an upper surface (31e) which seal a space surrounded by the first surface (31 a) to thethird surface (31 c).

According to a fifth aspect of the present invention, in any one of thefirst, second and third aspects of the present invention, a triangularprismatic housing (31) for each color light is arranged in proximity tothe color combination optical system (40), the triangular prismatichousing (31) for each color light having: a first surface (31 a) whichhas an inclination angle of approximately 45° with respect to an opticalaxis of each color light from each color light illuminating means(11-21) and on which the reflective polarizing plate (32) for each colorlight is attached; a second surface (31 b) which is orthogonal to theoptical axis of each color light transmitted through the reflectivepolarizing plate (32) for each color light and on which the reflectivespatial light modulation element (33) for each color light is attached;a third surface (31 c) which is orthogonal to the optical axis of eachcolor light obtained by reflecting reflected light from the reflectivespatial light modulation element (33) for each color light by thereflective polarizing plate (32) for each color and on which atransparent glass plate (36) for each color light is attached; and alower surface (31 d) and an upper surface (31 e) which seal a spacesurrounded by the first surface (31 a) to the third surface (31 c), andthe unnecessary polarized light removing means (37) for each color lightis secured on each incidence surface (40 a-40 c) of the colorcombination optical system (40) which faces the transparent glass plate(36) for each color light attached on the third surface (31 c) of thetriangular prismatic housing (31) for each color light.

According to a sixth aspect of the present invention, in any one of thefirst, second and third aspects of the present invention, a triangularprismatic housing (31) for the R light, a triangular prismatic housing(31) for the G light and a triangular prismatic housing (31) for the Blight are arranged in proximity to the color combination optical system(40), the triangular prismatic housing for the R light having: a firstsurface (31 a) which has an inclination angle of approximately 45° withrespect to an optical axis of the R light in the respective color lightsfrom each color light illuminating means (11-21) and on which areflective polarizing plate (32) for R light is attached; a secondsurface (31 b) which is orthogonal to the optical axis of the R lighttransmitted through the reflective polarizing plate (32) for the R lightand on which a reflective spatial light modulation element (33) for Rlight is attached; a third surface (31 c) which is orthogonal to theoptical axis of the R light obtained by reflecting reflected light fromthe reflective spatial light modulation element (33) for the R light bythe reflective polarizing plate (32) for the R light and on which atransparent glass plate (36) for R light is attached; and a lowersurface (31 d) and an upper surface (31 e) which seal a space surroundedby the first surface (31 a) to the third surface (31 c), the triangularprismatic housing (31) for the G light having: a first surface (31 a)which has an inclination angle of approximately 45° with respect to anoptical axis of the G light in the respective color lights from eachcolor light illuminating means (11-21) and on which a reflectivepolarizing plate (32) for G light is attached; a second surface (31 b)which is orthogonal to the optical axis of the G light transmittedthrough the reflective polarizing plate (32) for the G light and onwhich a reflective spatial light modulation element (33) for G light isattached; a third surface (31 c) which is orthogonal to the optical axisof the G light obtained by reflecting reflected light from thereflective spatial light modulation element (33) for the G light by thereflective polarizing plate (32) for the G light and on which atransparent glass (36) for G light is attached; and a lower surface (31d) and an upper surface (31 e) which seal a space surrounded by thefirst surface (31 a) to the third surface (31 c); the triangularprismatic housing (31) for the B light having: a first surface (31 a)which has an inclination angle of approximately 45° with respect to anoptical axis of the B light in the respective color lights from eachcolor light illuminating means (11-21) and on which a reflectivepolarizing plate (32) for B light is attached; a second surface (31 b)which is orthogonal to the optical axis of the B light transmittedthrough the reflective polarizing plate (32) for the B light and onwhich a reflective spatial light modulation element (33) for B light isattached; a third surface (31 c) which is orthogonal to the optical axisof the B light obtained by reflecting reflected light from thereflective spatial light modulation element (33) for the B light by thereflective polarizing plate (32) for the B light and on whichunnecessary polarized light removing means (35) for B light is attached;and a lower surface (31 d) and an upper surface (31 e) which seal aspace surrounded by the first surface (31 a) to the third surface (31c), and unnecessary polarized light removing means (37) for R light andG light are secured on respective incidence surfaces (40 a, 40 b) of thecolor combination optical system (40) which respectively face thetransparent glass plate (36) for the R light attached on the thirdsurface (31 c) of the triangular prismatic housing (31) for the R lightand the transparent glass plate (36) for the G light attached on thethird surface (31 c) of the triangular prismatic housing (31) for the Glight.

According to the fourth, fifth and sixth aspects of the presentinvention, since the inside of a triangular prismatic housing is sealedin a state where the reflective polarizing plate (a so-called “wire gridpolarizer”) is attached on a first surface of the triangular prismatichousing, the reflective spatial light modulation element (a reflectiveliquid crystal panel) is attached on a second surface of the triangularprismatic housing and the unnecessary polarized light removing means ora transparent glass plate is attached on a third surface of thetriangular surface, dust does not enter the triangular prismatichousing, thereby improving quality and reliability with respect to eachcomponent attached in the triangular prismatic housing.

According to a seventh aspect of the present invention, in any one ofthe first, second and third aspects of the present invention, atriangular prismatic housing (31) for each color light is arranged inproximity to the color combination optical system, the triangularprismatic housing (31) for each color light having: a first surface (31a) which has an inclination angle of approximately 45° with respect toan optical axis of each color light from each color light illuminatingmeans (11-21) and on which the reflective polarizing plate (32) for eachcolor light is attached; a second surface (31 b) which is orthogonal tothe optical axis of each color light transmitted through the reflectivepolarizing plate (32) for each color light and on which the reflectivespatial light modulation element (33) for each color light is attached;a third surface (31 c) which has a predetermined inclination angle withrespect to the optical axis of each color light obtained by reflectingreflected light from the reflective spatial light modulation element(33) for each color light by the reflective polarizing plate (32) foreach color light and on which the unnecessary polarized light removingmeans (34, (35)) for each color light is attached in order to preventunnecessary reflected light from the projection lens (42) side frombeing projected; and a lower surface (31 d) and an upper surface (31 a)which seal a space surrounded by the first surface (31 a) to the thirdsurface (31 c).

According to an eighth aspect of the present invention, in any one ofthe first, second and third aspects of the present invention, atriangular prismatic housing (31) for each color light is arranged inproximity to the color combination optical system (40), the triangularprismatic housing (31) for each color light having: a first surface (31a) which has an inclination angle of approximately 45° with respect toan optical axis of each color light from each color light illuminatingmeans (11-21) and on which the reflective polarizing plate (32) for eachcolor light is attached; a second surface (31 b) which is orthogonal tothe optical axis of each color light transmitted through the reflectivepolarizing plate (32) for each color light and on which the reflectivespatial light modulation element (33) for each color light is attached;a third surface (31 c) which has a predetermined inclination angle withrespect to the optical axis of each color light obtained by reflectingreflected light from the reflective spatial light modulation element(33) for each color light by the reflective polarizing plate (32) foreach color light and on which a transparent glass plate (36) for eachcolor light is attached in order to prevent unnecessary reflected lightfrom the projection lens (42) side from being projected; and a lowersurface (31 d) and an upper surface (31 e) which seal a space surroundedby the first surface (31 a) to the third surface (31 c), and theunnecessary polarized light removing means (37) for each color light issecured on each incidence surface (40 a, 40 b) of the color combinationoptical system (40) which faces the transparent glass plate (36) foreach color light attached on the third surface (31 a) of the triangularprismatic housing (31) for each color light.

According to a ninth aspect of the present invention, in any one of thefirst, second and third aspects of the present invention, a triangularprismatic housing (31) for R light, a triangular prismatic housing (31)for G light and a triangular prismatic housing (31) for B light arearranged in proximity to the color combination optical system (40), thetriangular prismatic housing for the R light having: a first surface (31a) which has an inclination angle of approximately 45° with respect toan optical axis of the R light in the respective color lights from eachcolor light illuminating means (11-21) and on which a reflectivepolarizing plate for R light is attached; a second surface (31 b) whichis orthogonal to the optical axis of the R light transmitted through thereflective polarizing plate (32) for the R light and on which areflective spatial light modulation element (33) for R light isattached; a third surface (31 c) which has a predetermined inclinationangle with respect to the optical axis of the R light obtained byreflecting reflected light from the reflective spatial light modulationelement (33) for the R light by the reflective polarizing plate (32) forthe R light and on which a transparent glass plate (36) for R light isattached in order to prevent unnecessary reflected light from theprojection lens (42) side from being projected; and a lower surface (31d) and an upper surface (31 e) which seal a space surrounded by thefirst surface (31 a) to the third surface (31 c), the triangularprismatic housing (31) for the G light having: a first surface (31 a)which has an inclination angle of approximately 45° with respect to anoptical axis of the G light in the respective color lights from eachcolor light illuminating means (11-21) and on which a reflectivepolarizing plate (32) for G light is attached; a second surface (31 b)which is orthogonal to the optical axis of the G light transmittedthrough the reflective polarizing plate (32) for the G light and onwhich a reflective spatial light modulation element (33) for G light isattached; a third surface (31 c) which has a predetermined inclinationangle with respect to the optical axis of the G light obtained byreflecting reflected light from the reflective spatial light modulationelement (33) for the G light by the reflective polarizing plate (32) forthe G light and on which a transparent glass plate (36) for G light isattached in order to prevent unnecessary reflected light from theprojection lens (42) side from being projected; and a lower surface (31d) and an upper surface (31 e) which seal a space surrounded by thefirst surface (31 a) to the third surface (31 c), the triangularprismatic housing (31) for the B light having: a first surface (31 a)which has an inclination angle of approximately 45° with respect to anoptical axis of the B light in the respective color lights from eachcolor light illuminating means (11-21) and on which a reflectivepolarizing plate for B light is attached; a second surface which isorthogonal to the optical axis of the B light transmitted through thereflective polarizing plate (32) for the B light and on which areflective spatial light modulation element (33) for B light isattached; a third surface (31 c) which has a predetermined inclinationangle with respect to the optical axis of the B light obtained byreflecting reflected light from the reflective spatial light modulationelement for the B light by the reflective polarizing plate (32) for theB light and on which unnecessary polarized light removing means (35) forB light is attached in order to prevent unnecessary reflected light fromthe projection lens (42) side from being projected; and a lower surface(31 d) and an upper surface (31 e) which seal a space surrounded by thefirst surface (31 a) to the third surface (31 c), and unnecessarypolarized light removing means (37) for R light and G light are securedon respective incidence surfaces (40 a, 40 b) of the color combinationoptical system (40) which respectively face the transparent glass plate(36) for the R light attached on the third surface (31 c) of thetriangular prismatic housing (31) for the R light and the transparentglass plate (36) for the G light attached on the third surface (31 c) ofthe triangular prismatic housing (31) for the G light.

According to the seventh, eighth and ninth aspects of the presentinvention, since the inside of the triangular prismatic housing issealed in a state where the reflective polarizing plate (a so-called“wire grid polarizer”) is attached on the first surface of thetriangular prismatic housing, the reflective spatial light modulationelement (a reflective liquid crystal panel) is attached on the secondsurface of the triangular prismatic housing and the unnecessarypolarized light removing means or a transparent glass plate is attachedon the third surface of the triangular prismatic housing which isinclined at a predetermined angle, dust does not enter the triangularprismatic housing, thereby improving quality and reliability withrespect to each component attached in the triangular prismatic housing.Further, since the unnecessary polarized light removing means or thetransparent glass plate obliquely attached on the third surface of thetriangular prismatic housing at a predetermined angle preventsunnecessary reflected light from the projection lens side from beingprojected, contrast is not lowered with respect to color-combined imagelight emitted from the projection lens, and a factor of displaying aghost image can be also removed, whereby the color-combined image lightwith high picture quality can be projected onto the screen.

According to a tenth aspect of the present invention, the unnecessarypolarized light removing means (34, (35), (37)) for each color light hasa function of restricting a disused wavelength band in any one of thefirst to ninth aspects of the present invention.

According to the tenth aspect of the present invention, since theunnecessary polarized light removing means for each color light has thefunction of restricting a disused wavelength band, it is possible toobtain a projected image with high color purity and improved contrast.

According to an eleventh aspect of the present invention, thetransparent glass plate (36) for each color light has a function ofrestricting a disused wavelength band in the fifth or eighth aspect ofthe present invention.

According to a twelfth aspect of the present invention, the transparentglass plate (36) for the R light and the G light has a function ofrestricting a disused wavelength band in the sixth or ninth aspect ofthe present invention.

According to the eleventh and twelfth aspects of the present invention,since the transparent glass plate for each color light and thetransparent glass plate for the R light and the G light have thefunction of restricting a disused wavelength band, it is possible toobtain a projected image with high color purity and improved contrast.

Furthermore, in order to achieve the above object, according to athirteenth aspect of the present invention, there is provided aprojection type display apparatus (10) comprising: a reflectivepolarizing plate (32) which has an inclination angle of approximately45° with respect to an optical axis of an incident light from a lightsource (11) and transmits a predetermined polarized light; a reflectivemodulation element (33) which modulates the predetermined polarizedlight from the reflective polarizing plate (32) and reflects themodulated polarized light; and a closed-type triangular prismatichousing (31) which has triangular upper and lower surfaces (31 d, 31 e)and first to third surfaces (31 a, 31 b, 31 c) connecting the uppersurface (31 e) and the lower surface (31 d), the reflective polarizingplate (32) and the reflective modulation element (33) being attached oninner surfaces of the first surface (31 a) and the second surface (31b), respectively, wherein a polarized light having a polarized lightcomponent orthogonal to the incident light included in a light reflectedon the reflective modulation element (33) is reflected on the reflectivepolarizing plate (32) and then emitted from the third surface (31 c) ofthe closed-type triangular prismatic housing (31).

According to a fourteenth aspect of the present invention, unnecessarypolarized light removing means (34, (35), (37)) attached on an innersurface of the third surface (31 c) of the closed-type triangularprismatic housing (31), for removing an unnecessary polarize light isfurther provided in the thirteenth aspect of the present invention.

According to a fifteenth aspect of the present invention, theunnecessary polarized light removing means (34, (35), (37)) is apolarizing plate (34, (37)) which absorbs the unnecessary polarizedlight or a polarizing plate (35) which reflects the unnecessarypolarized light in the fourteenth aspect of the present invention.

The nature, principle and utility of the invention will become moreapparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a structural view showing a conventional projection typedisplay apparatus;

FIG. 2 is a side view showing an arrangement of cooling fans in theconventional projection type display apparatus;

FIG. 3 is a perspective view showing a state of cooling a polarizer anda liquid crystal panel in the conventional projection type displayapparatus;

FIG. 4 is a plan view showing a configuration of a projection typedisplay apparatus of Embodiment 1 according to the present invention;

FIGS. 5A and 5B are a perspective view showing respective reflectiveliquid crystal panel assemblies for R, G and B lights and a three-colorcombination cross dichroic prism and a side view showing the three-colorcombination cross dichroic prism and the reflective liquid crystal panelassembly for the G light in the projection type display apparatus ofEmbodiment 1 according to the present invention;

FIG. 6 is a perspective view showing the reflective liquid crystaldisplay panel assembly for the R light, the G light or the B light in anenlarging manner in the projection type display apparatus of Embodiment1 according to the present invention;

FIGS. 7A to 7C are views illustrating a reflective polarizing plate inthe reflective liquid crystal panel assembly in the projection typedisplay apparatus of Embodiment 1 according to the present invention;

FIG. 8 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 1 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention;

FIGS. 9A and 9B are a perspective view showing respective reflectiveliquid crystal panel assemblies for R, G and B lights and a three-colorcombination cross dichroic prism and a side view showing the three-colorcombination cross dichroic prism and the reflective liquid crystal panelassembly for the G light in Modification 1 obtained by partiallymodifying the projection type display apparatus of Embodiment 1;

FIG. 10 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 2 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention;

FIGS. 11A and 11B are a perspective view showing respective reflectiveliquid crystal display panel assemblies for R, G and B lights and athree-color combination cross dichroic prism and a side view showing thethree-color cross dichroic prism and the reflective liquid crystal panelassembly for the G light in Modification 2 obtained by partiallymodifying the projection type display apparatus of Embodiment 1;

FIG. 12 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 3 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention;

FIGS. 13A and 13B are a perspective view showing respective reflectiveliquid crystal panel assemblies for R, G and B lights and a three-colorcombination cross dichroic prism and a side view showing the reflectiveliquid crystal panel assembly for the B light, the three-colorcombination cross dichroic prism and the reflective liquid crystal panelassembly for the R light in Modification 3 obtained by partiallymodifying the projection type display apparatus of Embodiment 1;

FIG. 14 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 4 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention;

FIGS. 15A and 15B are a perspective view showing respective reflectiveliquid crystal panel assemblies for R, G and B lights and a three-colorcombination cross dichroic prism and a side view showing the reflectiveliquid crystal panel assembly for the B light, the three-colorcombination cross dichroic prism and the reflective type liquid crystalpanel assembly for the R light in Modification 4 obtained by partiallymodifying the projection type display apparatus of Embodiment 1;

FIG. 16 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 5 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention;

FIGS. 17A and 17B are a perspective view showing respective reflectiveliquid crystal panel assemblies for R, G and B lights and a three-colorcombination cross dichroic prism and a side view showing the reflectiveliquid crystal panel assembly for the B light, the three-colorcombination cross dichroic prism and the reflective liquid crystal panelassembly for the R light in Modification 5 obtained by partiallymodifying the projection type display apparatus of Embodiment 1;

FIG. 18 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 6 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention;

FIGS. 19A and 19B are a perspective view showing respective reflectiveliquid crystal panel assemblies for R, G and B lights and a three-colorcombination cross dichroic prism and a side view showing the three-colorcombination cross dichroic prism and the reflective liquid crystal panelassembly for the G light in Modification 6 obtained by partiallymodifying the projection type display apparatus of Embodiment 1;

FIG. 20 is a perspective view showing the reflective liquid crystalpanel assembly for the R light, the G light or the B light in anenlarging manner in Modification 6 obtained by partially modifying theprojection type display apparatus of Embodiment 1;

FIG. 21 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 7 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention;

FIGS. 22A and 22B are a perspective view showing respective reflectiveliquid crystal panel assemblies for R, G and B lights and a three-colorcombination cross dichroic prism and a side view showing the three-colorcombination cross dichroic prism and the reflective liquid crystal panelassembly for the G light in Modification 7 obtained by partiallymodifying the projection type display apparatus of Embodiment 1;

FIG. 23 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 8 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention;

FIGS. 24A and 24B are a perspective view showing respective reflectiveliquid crystal panel assemblies for R, G and B lights and a three-colorcombination cross dichroic prism and a side view showing the three-colorcombination cross dichroic prism and the reflective liquid crystal panelassembly for the G light in Modification 8 obtained by partiallymodifying the projection type display apparatus of Embodiment 1;

FIG. 25 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 9 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention;

FIGS. 26A and 26B are a perspective view showing respective reflectiveliquid crystal panel assemblies for R, G and B lights and a three-colorcombination cross dichroic prism and a side view showing the reflectiveliquid crystal panel assembly for the B light, the three-colorcombination cross dichroic prism and the reflective liquid crystal panelassembly for the R light in Modification 9 obtained by partiallymodifying the projection type display apparatus of Embodiment 1;

FIG. 27 is a plan view showing a configuration of a projection typedisplay apparatus of Embodiment 2 according to the present invention;

FIG. 28 is a side view showing a three-color combination prism and areflective liquid crystal panel assembly for G light in the projectiontype display apparatus of Embodiment 2 according to the presentinvention;

FIG. 29 is a perspective view showing a configuration of a projectiontype display apparatus of Embodiment 3 according to the presentinvention;

FIG. 30 is a plan view showing the configuration of the projection typedisplay apparatus of Embodiment 3 according to the present invention;and

FIGS. 31A and 31B are a perspective view showing respective reflectiveliquid crystal panel assemblies for R, G and B lights and a three-colorcross dichroic prism and an X-X cross-sectional view showing thereflective liquid crystal panel assembly for the R light, thethree-color combination cross dichroic prism and the reflective liquidcrystal panel assembly for the B light in the projection type displayapparatus of Embodiment 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of a projection type display apparatus according to thepresent invention will now be described in detail hereinafter in theorder of Embodiments 1 to 3 with reference to the accompanying drawings.

Embodiment 1

FIG. 4 is a plan view showing a configuration of a projection typedisplay apparatus of Embodiment 1 according to the present invention.FIGS. 5A and 5B are a perspective view showing respective reflectiveliquid crystal panel assemblies for R, G and B lights and a three-colorcombination cross dichroic prism and a side view showing the three-colorcombination cross dichroic prism and the reflective liquid crystal panelassembly for the G light in the projection type display apparatus ofEmbodiment 1 according to the present invention. FIG. 6 is a perspectiveview showing the reflective liquid crystal panel assembly for the Rlight, the G light or the B light in the projection type displayapparatus of Embodiment 1 according to the present invention. FIGS. 7Ato 7C are views illustrating a reflective polarizing plate in thereflective liquid crystal panel assembly in the projection type displayapparatus of Embodiment 1 according to the present invention.

As shown in FIG. 4, a projection type display apparatus 10 of Embodiment1 according to the present invention is constituted by using areflection type which reflects light as each spatial light modulationelement corresponding to R light, G light or B light as will bedescribed later. In this projection type display apparatus 10, on thesame plane are arranged a light source 11 which emits white light asnon-polarized light, color separation optical systems 17 and 19 whichsubject the white light from the light source 11 to color separation toobtain the R light (red light), the G light (green light) and the Blight (blue light), respective reflective spatial light modulationelements (which will be referred to as reflective liquid crystal panelshereinafter) 33 for the R, G and B lights, a three-color combinationcross dichroic prism 40 which performs color combination of image lightshaving the respective colors subjected to light modulation by therespective reflective liquid crystal panels 33 for the R, G and Blights, and a projection lens 42 which projects color-combined imagelight obtained by the three-color combination cross dichroic prism 40.

First, the light source 11 emits white light as non-polarized lightincluding the R light, the G light and the B light by using, e.g., ametal halide lamp, a xenon lamp or a halogen lamp. When the white lightemitted from this light source 11 is reflected by a concave sphericalreflecting mirror 12, the white source is turned to each parallel lightto sequentially enter a first fly-eye lens array 13 attached on a frontsurface of the concave spherical reflecting mirror 12 and a secondfly-eye lens array 14 provided in front of this first fly-eye lens array13. These first and second fly-eye lens arrays 13 and 14 form a pair toconstitute an integrator which homogenizes an illumination distributionwithin a light beam of the white light. It is to be noted that anon-illustrated visible external light removing filter which cutsultraviolet light and infrared light may be arranged in front of thelight source 11.

Then, the non-polarized white light whose illumination distribution hasbeen homogenized by the first and second fly-eye lens arrays 13 and 14is allowed to enter a polarization converting prism array 15 as apolarization converting optical element. This polarization convertingprism array 15 has a polarization split prism array and a λ/2 waveplate, and is constituted into a tabular shape as a whole. That is,light which has entered this polarization converting prism array 15 isfirst divided into a P polarized component and an S polarized componentwith respect to polarizing beam splitter film surfaces by the polarizingbeam splitter film surfaces of the polarization split prism array. Atthis time, the plurality of polarizing beam splitter film surfaces ofthe polarization converting prism array 15 are provided in the form ofparallel strips, and each film surface has an inclination ofapproximately 45° with respect to a main surface of the polarizationconverting prism array 15. The P polarized component is transmittedthrough the polarizing beam splitter film surfaces to be emitted to afront surface side of the polarization converting prism array 15, andthe S polarized component is reflected by the polarizing beam splitterfilm surfaces. An optical path of the S polarized component reflected byone polarizing beam splitter film surface is deflected 90°. This Spolarized component is again reflected by an adjacent polarizing beamsplitter film surface so that its optical path is deflected 90°, and isemitted to the front surface side of the polarization converting prismarray 15. Furthermore, the λ/2 wave plate is provided in a region towhich such an S polarized component is emitted. A polarization directionof the S polarized component transmitted through this λ/2 wave plate isrotated 90° so that the S polarized component has the same polarizationdirection as that of the P polarized component transmitted through thepolarizing beam splitter film surfaces (or the S polarized componentreflected twice by the polarizing beam splitter film surfaces). Afterthe non-polarized white light from the light source 11 is transmittedthrough the polarization converting prism array 15 in this manner, thewhite light is turned to polarized light in a predetermined direction.

In this Embodiment 1, the light transmitted through the polarizationconverting prism array 15 is converted into, e.g., P polarized light asthe polarized light in a predetermined direction as indicated by a signin FIG. 4. However, polarization converting efficiency in thepolarization converting prism array 15 is not 100%, and the S polarizedcomponent of several % to several-ten % is included in the light emittedfrom this polarization converting prism array 15.

It is to be noted that a description will be given as to the polarizedlight in a predetermined direction obtained by the polarizationconverting prism array 15 as the P polarized light, but the presentinvention is not restricted thereto, and it is possible to adopt amethod which subjects the white light from the light source 11 topolarization conversion to be turned to the S polarized light in thelight converting prism array 15.

Then, the white light as the P polarized light transmitted through thepolarization converting prism array 15 enters the first dichroic mirror17 through a field lens 16. This first dichroic mirror 17 reflects twocolor components, i.e., the R light and the G light from the white lightincluding the R light, the G light and the B light so that theirdirection is changed 90°, and transmits the remaining B lighttherethrough so that the B light travels straight ahead. Additionally,the R light and the G light reflected by the first dichroic mirror 17fall on a first metal film reflecting mirror 18 to be reflected by thisfirst metal film reflecting mirror 18 so that their direction is changed90°. Thereafter, these lights enter or fall on the second dichroicmirror 19. In this second dichroic mirror 19, the R light is transmittedtherethrough to travel straight ahead so that the R light enters areflective liquid crystal panel assembly 30R for the R light and, on theother hand, the G light is reflected so that its direction is changed90°, and the G light then enters a reflective liquid crystal panelassembly 30G for the G light.

Further, the B light transmitted through the first dichroic mirror 17 issequentially reflected by second and third metal film reflecting mirrors20 and 21 to enter a reflective liquid crystal panel assembly 30B forthe B light.

The first and second dichroic mirrors 17 and 19 constitute colorseparation optical systems which subject the white light from the lightsource 11 to color separation to be divided into the R light, the Glight and the B light, and the respective constituent members from thelight source 11 to the color separation optical systems 17 and 19constitute respective color light illuminating means which illuminatethe reflective liquid crystal panels (reflective spatial lightmodulation elements) 33 for the respective color lights with the Rlight, the G light and the B light.

It is to be noted that the description has been given as to the examplein which the white light from the light source 11 is subjected to colorseparation to be divided into the R light, the G light and the B lightby the color separation optical systems 17 and 19 in this Embodiment 1,but the present invention is not restricted thereto. For example, whenrespective LED light sources for the R light, the G light and the Blight which emit the R light, the G light and the B light are used, thecolor separation optical systems 17 and 19 do not have to be provided,and hence the respective reflective liquid crystal panels 33 for therespective color lights corresponding to the respective color lights maybe directly illuminated with the respective polarized components in onedirection of the R light, the G light and the B light emitted from theLED light sources for the respective color lights as respective colorlight illuminating means. Furthermore, the LED light sources for therespective color lights as the respective color light illuminating meanscan be applied to later-described Modifications 1 to 9 obtained bypartially modifying Embodiment 1, a later-described Embodiment 2 and alater-described Embodiment 3.

Here, the reflective liquid crystal panel assembly 30R for the R light,the reflective liquid crystal panel assembly 30G for the G light and thereflective liquid crystal panel assembly 30B for the B light all havethe same configuration, and the reflective liquid crystal panel assembly30R for the R light, the reflective liquid crystal panel 30G for the Glight and the reflective liquid crystal panel assembly 30B for the Blight respectively face respective incidence surfaces 40 a to 40 c ofthe three-color combination cross dichroic prism 40 as a colorcombination optical system having a rectangular parallelepiped shapewith respective gaps therebetween.

In this example, as shown in FIGS. 5A and 5B, the reflective liquidcrystal panel assembly 30R for the R light, the reflective liquidcrystal panel assembly 30G for the G light, the reflective liquidcrystal panel assembly 30B for the B light and the three-colorcombination cross dichroic prism 40 are fixed on an upper surface 25 aof a base board 25 using an aluminum material or the like by anadhesive.

Furthermore, as shown in FIG. 6 in an enlarging manner, in each of thereflective liquid crystal panel assembly 30R for the R light, thereflective liquid crystal panel assembly 30G for the G light and thereflective liquid crystal panel assembly 30B for the B light, a hollowtriangular prismatic housing 31 is prepared for each color light, atabular reflective polarizing plate (a sol-called “wire grid polarizer”)32 as polarization splitting means is attached on a first surface 31 ahaving an inclination angle of approximately 45° with respect to anoptical axis of each color light from each color light illuminatingmeans from the light source (FIG. 4) to the color separation opticalsystems 17 and 19 (FIG. 4) in the triangular prismatic housing for eachcolor light, a reflective liquid crystal panel 33 is attached on asecond surface 31 b orthogonal to the optical axis of each color lighttransmitted through the reflective polarizing plate 32 for each colorlight, a transmission type polarizing plate 34 as unnecessary polarizedlight removing means is attached on a third surface 31 c orthogonal tothe optical axis of each color light obtained by reflecting reflectedlight from the reflective liquid crystal panel 33 for each color lightby the reflective polarizing plate 32 for each color light, and eachside on which the transmission type polarizing plate 34 for each colorlight is arranged faces each of the incidence surfaces 40 a to 40 c(FIGS. 4, 5A and 5B) of the three-color combination cross dichroic prism40 with a gap therebetween in a state where a space surrounded by thefirst surface 31 a to the third surface 31 c of the triangular prismatichousing 31 is sealed from dust or the like by a lower surface 31 d andan upper surface 31 e.

It is to be noted that the triangular prismatic housing 31 is alsoapplied to later-described Modifications 1 to 3 obtained by partiallymodifying Embodiment 1.

In this example, the reflective polarizing plate 32, the reflectiveliquid crystal panel 33 and the transmission type polarizing plate 34respectively attached on the triangular prismatic housing 31 for eachcolor are vertically provided with respect to an upper surface 25 a ofthe base board 25 (FIGS. 5A and 5B).

Further, a wave plate 33 a which corrects the liquid crystalcorresponding to a pre-tilt by reciprocation is attached on a frontsurface of the reflective liquid crystal panel 33, and a heat sink 33 bwhich cools the reflective liquid crystal panel 33 is attached on a rearsurface of this reflective liquid crystal panel 33.

Furthermore, for example, when the R light of the P polarized componententers the reflective liquid crystal panel assembly 30R for the R light,this R light of the P polarized component is transmitted through thereflective polarizing plate 32 attached on the triangular prismatichousing 31 to enter the reflective liquid crystal panel 33 for the Rlight.

Moreover, as shown in FIG. 7A, the reflective polarizing plate 32 whichis also referred to as the “wire grid polarizer” is formed by regularlyarranging a plurality of metal wires 32 b of aluminum or the like in astrip form on an optical glass plate 32 a at a pitch of, e.g., 140 nm,and has a function of transmitting a polarized component (e.g., the Ppolarized light) vertical to the metal wires 32 b therethrough and afunction of reflecting a polarized component (e.g., the S polarizedlight) parallel to the metal wires 32 b.

Additionally, as shown in FIG. 7B, assuming that an incidence angle α ofincident light based on the P polarized light with respect to thereflective polarizing plate 32 is a parameter, FIG. 7C shows wavelengthdependence of a transmission factor of the P polarized component. Inthis FIG. 7C, a indicates a case where the incidence angle α of theincident light based on the P polarized light with respect to thereflective polarizing plate 32 is 0°, b indicates a case where theincidence angle α is −15°, and c indicates a case where the incidenceangle α is +15°. It is to be noted that the incidence angle α is anangle formed by the incident light on the reflective polarizing plate 32with respect to the optical axis, and an incidence surface of thereflective polarizing plate 32 is inclined approximately 45° withrespect to the optical axis. In this reflective polarizing plate 32,even if the incidence angle α reaches ±15°, the wavelength dependence ofa transmission factor of the P polarized light is very small and stablein a visible wavelength region.

Therefore, it can be understood that a bright display image withexcellent color reproducibility can be obtained when the reflectivepolarizing plate 32 is used. Additionally, since the reflectivepolarizing plate 32 is one tabular polarization splitting plate, it islight in weight. Further, since the reflective polarizing plate 32hardly absorbs light emitted from the light source 11 (FIG. 4), it cansuppress a reduction in quality of a display image due to birefringence.

Again referring to FIGS. 4, 5A and 5B, when the R light based on the Ppolarized light transmitted through the reflective polarizing plate 32for the R light enters the reflective liquid crystal panel 33 for the Rlight, a light beam reflected after being subjected to light modulationin accordance with an image signal of the R light in the reflectiveliquid crystal panel 33 for the R light through the wave plate 33 aattached on the surface of the reflective liquid crystal panel 33 isagain transmitted through the wave plate 33 a to return to thereflective polarizing plate 32 for the R light. Here, only a light beamof the S polarized light which has been light-modulated and reflected bythe reflective liquid crystal panel 33 for the R light is reflected bythe reflective polarizing plate 32 for the R light.

In this example, the reflective liquid crystal panel 33 has a reflectiontype configuration in which switching elements are provided on a siliconsubstrate in a matrix form, a plurality of pixel electrodes formed of ametal such as aluminum are provided in a matrix form on the switchingelements through an insulating layer, a liquid crystal is includedbetween the plurality of pixel electrodes and a common electrodeprovided on a transparent substrate, a voltage is applied between theplurality of pixel electrodes and the common electrode, incident lightwhich has entered from the transparent substrate side is subjected tolight modulation in accordance with an image signal of each color light,and image light obtained by reflecting this incident light by theplurality of pixel electrodes is emitted. Such a reflective liquidcrystal panel 33 has a high degree of pixel integration and hence it issuitable for a high-resolution image. Further, it has an advantage thata numerical aperture can be increased to approximately 90% and a bright,smooth and fine image can be displayed since a circuit structure can belaminated below the plurality of pixel electrodes.

Then, the R light based on the S polarized light reflected by thereflective polarizing plate 32 for the R light enters the transmissiontype polarizing plate 34 as the unnecessary polarized light removingmeans for the R light arranged to face the three-color combination crossdichroic prism 40 in the triangular prismatic housing 31 for the Rlight, and the R light is allowed to enter from the incidence surface 40a of the three-color combination cross dichroic prism 40 while removingthe P polarized light (the unnecessary polarized light) which is anunwanted polarized component in this transmission type polarizing plate34.

In this example, the transmission type polarizing plate 34 as theunnecessary polarized light removing means is provided in order toremove the unnecessary P polarized light since the P polarized light asthe unnecessary polarized light can be a factor of lowering a contrastratio of a display image if the P polarized light is mixed in thereflected light from the reflective polarizing plate 32. Furthermore, asthe transmission type polarizing plate 34, absorption dichroism isobtained by performing dyeing and absorption of a dichroic material suchas iodine or an organic dye in a base material film (polyvinyl alcohol;PVA) and highly drawing and orienting the obtained material. Apolarizing film in which this PVA polarizing layer is held between TAC(triacetylcellulose) layers is attached on a glass substrate by a binderor an adhesive. The transmission type polarizing plate 34 having suchabsorption dichroism as a fundamental principle absorbs a polarizedcomponent in the same direction as an array of a dichroic dye andtransmits the other polarized component of orthogonal polarizedcomponents of an incident light beam.

Since this transmission type polarizing plate 34 is of a lightabsorption type, it is desirable to constitute this plate by using asubstrate of, e.g., crystal or sapphire superior in thermal conductivitywhile considering heat resisting properties and heat radiatingproperties. In order to improve a light utilization ratio and avoid areduction in quality of a display image due to unwanted reflected lighton an interface, a reflection reducing coat must be applied to an airinterface of the transmission type polarizing plate 34. It is desirableto optimize these polarization characteristics and antireflective coatcharacteristics with respect to each of the R, G and B colors.

Furthermore, although the transmission type polarizing plate 34 maycomprise a single-sided film, it is difficult to flatten a surface ofthe film in wavelength order, and hence non-planarity of this filmsurface becomes a wavefront aberration, which can be a factor ofdeteriorating a resolution. Thus, in order to realize a higherresolution, this polarizing film is held between flat substrates (whitesheet glass, optical glass, crystal, quartz, sapphire and others)subjected to optical polishing, and irregularities of the film arefilled with an adhesive or an adhesive compound, thereby preventing theresolution from being deteriorated.

Then, like the R light, when the G light and the B light are allowed toenter the reflective liquid crystal panel assembly 30G for the G lightand the reflective liquid crystal panel assembly 30B for the B light,the G light and the B light of the S polarized light which has beenlight-modulated and reflected by the reflective liquid crystal panels 33and 33 for the G light and the B light are allowed to enter from theincidence surface 40 b and the incidence surface 40 c of the three-colorcombination cross dichroic prism 40.

Thereafter, the respective image lights of the R light, the G light andthe B light which have entered from the respective incidence surfaces 40a to 40 c of the three-color combination cross dichroic prism 40 aresubjected to color combination by first and second dichroic films 40 eand 40 f formed in the three-color combination cross dichroic prism 40,color-combined image light obtained by this three-color cross dichroicprism 40 is emitted from an emission surface 40 d to enter a projectionlens 42 through a ¼ wave plate 41, and the color-combined image lightfrom which unnecessary polarized light has been removed by thetransmission type polarizing plate 34 is projected onto anon-illustrated screen by the projection lens 42. Therefore, highluminance and high contrast can be achieved, thereby contributing to animprovement in quality and reliability of the projection type displayapparatus 10.

In this example, the three-color combination cross dichroic prism 40 isformed into a rectangular parallelepiped shape (including a cubic shape)by using optical glass, and the first and second dichroic films 40 e and40 f cross each other in an X-like shape as seen from the upper surface.

Moreover, the first dichroic film 40 e in the three-color combinationcross dichroic prism 40 is provided with a function of reflecting the Rlight which has entered from the incidence surface 40 a and changing adirection of this light 90° so that this light is emitted from theemission surface 40 d, of transmitting the G light which has enteredfrom the incidence surface 40 b therethrough so that this light isemitted from the emission surface 40 d, and of also transmitting the Blight which has entered from the incidence surface 40 c therethrough.Additionally, the second dichroic film 40 f of the three-colorcombination cross dichroic prism 40 is provided with a function ofreflecting the B light which has entered from the incidence surface 40 cand changing a direction of this light 90° so that this light existsfrom the emission surface 40 d, of transmitting the G light which hasentered from the incidence surface 40 b therethrough so that this lightis emitted from the emission surface 40 d, and of also transmitting theR light which has entered from the incidence surface 40 a therebetween.Therefore, three-color combination is enabled by the first and seconddichroic films 40 e and 40 f formed in the three-color combination crossdichroic prism 40.

Further, the ¼ wave plate 41 arranged between the three-colorcombination cross dichroic prism 40 and the projection lens 42 preventsappearance of unwanted light in a ghost-like form which occurs when asmall quantity of reflected light from the lens surface of theprojection lens 42 returns to the reflective liquid crystal panel 33side for each color light through the three-color combination crossdichroic prism 40, the transmission type polarizing plate 34 for eachcolor light and the reflective polarizing plate 32 for each color light,and is again reflected to reach the screen. This ¼ wave plate 41 may beset as required.

Here, in Embodiment 1, when the R light, the G light and the B light areallowed to enter the reflective liquid crystal panel assembly 30R forthe R light, the reflective liquid crystal panel assembly 30G for the Glight and the reflective liquid crystal panel assembly 30B for the Blight, temperatures are increased in the reflective polarizing plate 32,the reflective liquid crystal panel 33 and the transmission typepolarizing plate 34 respectively attached and arranged on the triangularprismatic housing 31 for each color light whose inside is sealed and inthe respective incidence surfaces 40 a to 40 c of the three-colorcombination cross dichroic prism 40 due to the light from the lightsource 11. Therefore, a fan 26 as air-cooling means is rotatably set ona lower surface 25 b side of the base board 25.

Based on this configuration, a first fan hole 25 c is formed through thebase board 25 in accordance with each gap formed between the respectivereflective liquid crystal panel assemblies 30R, 30G and 30B for therespective color lights and the respective incidence surfaces 40 a to 40c of the three-color combination cross dichroic prism 40, and a secondfan hole 25 d is formed through the base board 25 so as to face the heatsink 33 b attached on the rear surface of the reflective liquid crystalpanel 33 for each color light.

Further, air stream W generated when rotating the fan 26 is supplied tothe upper surface 25 a side of the base board 25 through the first andsecond fan holes 25 c and 25 d formed in the base board 25 from thelower surface 25 b side of this base board 25. Here, the air stream Wwhich has passed through the first fan hole 25 c is supplied to each gapformed between the transmission type polarizing plate 34 attached on thetriangular prismatic housing 31 for each color light and the respectiveincidence surfaces 40 a to 40 c of the three-color combination crossdichroic prism 40 to cool the surface of the transmission typepolarizing plate 34 for each color light and the respective incidencesurfaces 40 a to 40 c of the three-color combination cross dichroicprism 40, and the air stream W which has passed through the second fanhole 25 d cools the heat sink 33 b attached on the rear surface of thereflective liquid crystal panel 33 for each color light. Therefore, itis possible to suppress an increase in temperatures of the reflectiveliquid crystal panel 33 for each color light, the transmission typepolarizing plate 34 for each color light and the three-color combinationcross-dichroic prism 40 to avoid deterioration due to heat generation,whereby high luminance and high contrast can be achieved, whichcontributes an improvement in reliability with respect to the projectiontype display apparatus 10 of Embodiment 1.

A projection type display apparatus 10A of Modification 1 obtained bypartially modifying the projection type display apparatus 10 ofEmbodiment 1 will now be briefly described while mainly focusing ondifferences from Embodiment 1 (FIGS. 4, 5A and 5B) with reference toFIGS. 8, 9A and 9B.

FIG. 8 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 1 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention. FIGS. 9 a and 9B are a perspective view showingrespective reflective liquid crystal panel assemblies for R, G and Blights and a three-color combination cross dichroic prism and a sideview showing the three-color combination cross dichroic prism and thereflective liquid crystal panel assembly for the G light in Modification1 obtained by partially modifying the projection type display apparatusof Embodiment 1.

As shown in FIGS. 8, 9A and 9B, in the projection type display apparatus10A of Modification 1 obtained by partially modifying Embodiment 1, adifference from Embodiment 1 lies in that a reflective polarizing plate35 for each color light which reflects unnecessary polarized light isused as unnecessary polarized light removing means for each color lightin place of the transmission type polarizing plate 34 for each colorlight utilized in Embodiment 1 in a reflective liquid crystal panelassembly 30R′ for R light, a reflective liquid crystal panel assembly30G′ for G light and a reflective liquid crystal panel assembly 30B′ forB light.

That is, in Modification 1 of Embodiment 1, each of the reflectiveliquid crystal panel assembly 30R′ for the R light, the reflectiveliquid crystal panel assembly 30G′ for the G light and the reflectiveliquid crystal panel assembly 30B′ for the B light has the followingconfiguration. A hollow triangular prismatic housing 31 is firstprepared for each color light and, in the triangular prismatic housing31 for each color light, a tabular reflective polarizing plate 32 (aso-called “wire grid polarizer”) as polarization splitting means isattached on a first surface 31 a (FIG. 6) having an inclination angle ofapproximately 45° with respect to an optical axis of each color lightfrom each color light illuminating means from a light source 11 to colorseparation optical systems 17 and 19, and a reflective liquid crystalpanel 33 is attached on a second surface 31 b (FIG. 6) orthogonal to theoptical axis of each color light transmitted through the reflectivepolarizing plate 32 for each color light. This point is the same asEmbodiment 1. However, a difference from Embodiment 1 lies in that thereflective polarizing plate 35 as the unnecessary polarized lightremoving means is attached on a third surface 31 c (FIG. 6) orthogonalto the optical axis of each color light obtained by reflecting reflectedlight from the reflective liquid crystal panel 33 for each color lightby the reflective polarizing plate 32 for each color light in place ofthe transmission type polarizing plate 34 (FIGS. 4, 5A and 5B) ofEmbodiment 1, and that each side on which the reflective polarizingplate 35 for each color light is provided faces each of incidencesurfaces 40 a to 40 c of a three-color combination cross dichroic prism40 with a gap therebetween.

In this example, as the reflective polarizing plate 35 which serves asthe unnecessary polarized light removing means, for example, a wire gridpolarizer is used, and this wire grid polarizer is superior in heatresisting properties or light stability as compared with thetransmission type polarizing plate 34 which is of a light absorptiontype used in Embodiment 1, thereby obtaining sufficient reliability withrespect to light from the high-power light source 11.

Therefore, in Modification 1 of Embodiment 1, unnecessary polarizedlight (P polarized light) other than S polarized light is removed by thereflective polarizing plate 35 for each color light with respect toimage light of each color from the reflective liquid crystal panel 33for each color light reflected by the reflective polarizing plate 32 foreach color light, and the S polarized light is emitted. Thereafter, theimage light of each color transmitted through the reflective polarizingplate 35 for each color light is subjected to color combination by thethree-color combination cross dichroic prism 40.

Then, in Modification 1 of Embodiment 1, an air stream W generated whenrotating a fan 26 is likewise supplied to an upper surface 25 a side ofa base board 25 through first and second fan holes 25 c and 25 d formedin this base board 25 from a lower surface 25 b side of the base board25. Here, the air stream W which has passed through the first fan hole25 c is supplied to each gap formed between the reflective polarizingplate 35 attached in the triangular prismatic housing 31 for each colorlight and each of the incidence surfaces 40 a to 40 c of the three-colorcombination cross dichroic prism 40 to cool a surface of the reflectivepolarizing plate 35 for each color light and each of the incidencesurfaces 40 a to 40 c of the three-color combination cross dichroicprism 40, and the air stream W which has passed through the second fanhole 25 d cools a heat sink 33 b attached on a rear surface of thereflective liquid crystal panel 33 for each color light. Therefore, itis possible to suppress an increase in temperatures of the reflectiveliquid crystal panel 33 for each color light, the reflective polarizingplate 35 for each color light and the three-color combination crossdichroic prism 40 to assuredly avoid deterioration due to heatgeneration, and high luminance and high contrast can be therebyachieved, which can contribute to an improvement in reliability withrespect to the projection type display apparatus 10A of Modification 1.

A projection type display apparatus 10B obtained by partially modifyingthe projection type display apparatus 10 of Embodiment 1 will now bebriefly described while mainly focusing on a difference from Embodiment1 (FIGS. 4, 5A and 5B) with reference to FIGS. 10, 11A and 11B.

FIG. 10 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 2 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention. FIGS. 11A and 11B are a perspective view showingrespective reflective liquid crystal panel assemblies for R, G and Blights and a three-color combination cross dichroic prism and a sideview showing the three-color combination cross dichroic prism and thereflective liquid crystal panel assembly for the G light in Modification2 obtained by partially modifying the projection type display apparatusof Embodiment 1.

As shown in FIGS. 10, 11A and 11B, in the projection type displayapparatus 10B of Modification 2 obtained by partially modifyingEmbodiment 1, a difference from Embodiment 1 lies in a reflective liquidcrystal panel assembly 30R″ for R light, a reflective liquid crystalpanel assembly 30G″ for G light and reflective liquid crystal panelassembly 30B″ for B light and a transmission type polarizing plate 37which is of a light absorption type and secured as unnecessary polarizedlight removing means for each color on each of incidence surfaces 40 ato 40 c of a three-color combination cross dichroic prism 40.

That is, in Modification 2 of Embodiment 1, each of the reflectiveliquid crystal panel assembly 30R″ for the R light, the reflectiveliquid crystal panel assembly 30G″ for the G light and the reflectiveliquid crystal panel assembly 30B″ for the B light has the followingconfiguration. A hollow triangular prismatic housing 31 is firstprepared for each color light and, in the triangular prismatic housing31 for each color light, a tabular reflective polarizing plate (aso-called “wire grid polarizer”) 32 as polarization splitting means isattached on a first surface 31 a (FIG. 6) having an inclination angle ofapproximately 45° with respect to an optical axis of each color lightfrom each color light illuminating means from a light source 11 to colorseparation optical systems 17 and 19, and a reflective liquid crystalpanel 33 is attached on a second, surface 31 b (FIG. 6) orthogonal tothe optical axis of each color light transmitted through the reflectivepolarizing plate 32 for each color light. This point is the same asEmbodiment 1. However, a difference from Embodiment 1 lies in that atransparent glass plate 36 is attached in place of the transmission typepolarizing plate 34 (FIGS. 4, 5A and 5B) of Embodiment 1 on a thirdsurface 31 c (FIG. 6) orthogonal to the optical axis of each color lightobtained by reflecting reflected light from the reflective liquidcrystal panel 33 for each color light by the reflective polarizing plate32 for each color light and a side on which the transparent glass plate36 for each color light is arranged faces each of incidence surfaces 40a to 40 c of a three-color combination cross dichroic prism 40 with agap therebetween. In this example, the transparent glass plate 36 foreach color light attached on the third surface 31 c (FIG. 3) of thetriangular prismatic housing 31 for each color light transmitstherethrough each color light obtained by reflecting the reflected lightfrom the reflective liquid crystal panel 33 for each color light by thereflective polarizing plate 32 for each color light so that thetransmitted light is emitted to the three-color combination crossdichroic prism 40 side, but the inside of the triangular prismatichousing 31 for each color light can be sealed from dust by attaching thetransparent glass plate 36 for each color light.

In Modification 2 of Embodiment 1, the reflective polarizing plate 32,the reflective liquid crystal panel 33 and the transparent glass plate36 attached and arranged in the triangular prismatic housing 31 for eachcolor light are likewise vertically provided with respect to an uppersurface 25 a of a base board 25.

Based on this configuration, the transmission type polarizing plate 37which is of a light absorption type as the unnecessary polarized lightremoving means for each color light which removes unnecessary polarizedlight with respect to each color light transmitted through thetransparent glass plate 36 for each color light is secured on each ofincidence surfaces 40 a to 40 c of the three-color combination crossdichroic prism 40.

In this example, the most inexpensive method of realizing thetransmission type polarizing plate 37 is directly securing atransmission type polarizing film on each of the incidence surfaces 40 ato 40 c of the three-color combination cross dichroic prism 40.Alternatively, the transmission type polarizing film may be secured on atransparent substrate and then further secured on each of the incidencesurfaces 40 a to 40 c. In this case, although inexpensive glass is usedas a material of the transparent substrate of the transmission typepolarizing plate 37, using crystal or sapphire superior in thermalconductivity can rapidly disperse heat of the polarizing film in thetransparent substrate surface and further efficiently transfer this heatto the three-color combination cross dichroic prism 40, therebyimproving reliability.

Therefore, in Modification 2 of Embodiment 1, image light of each colorfrom the reflective liquid crystal panel 33 for each color lightreflected by the reflective polarizing plate 32 for each color light isemitted from the transparent glass plate 36 for each color light as itis, then unnecessary polarized light (P polarized light) other than Spolarized light is removed by the transmission type polarizing plate 37for each color light secured on each of the incidence surface 40 a to 40c of the three-color combination cross dichroic prism 40 with respect tothe image light of each color transmitted through the transparent glassplate 36 for each color light, and the image light of each colortransmitted through the transmission type polarizing plate 37 for eachcolor light is subjected to color combination by the three-colorcombination cross dichroic prism 40.

Here, in Modification 2 of Embodiment 1, when the R light, the G lightand the B light are allowed to enter the reflective liquid crystal panelassembly 30R″ for the R light, the reflective liquid crystal panelassembly 30G″ for the G light and the reflective liquid crystal panelassembly 30B″ for the B light, light from the light source 11 increasestemperatures of the reflective polarizing plate 32, the reflectiveliquid crystal panel 33 and the transparent glass plate 36 attached onthe triangular prismatic housing 31 for each color light whose inside issealed, and the light from the light source 11 also increases atemperature of the transmission type polarizing plate 37 for each colorlight secured on each of the incidence surfaces 40 a to 40 c of thethree-color combination cross dichroic prism 40. Therefore, in order toavoid an increase in temperatures of these optical members, a coolingfan 26 is rotatably set on a lower surface 25 b side of a base board 25as shown in FIGS. 11A and 11B.

Based on this configuration, a first fan hole 25 c is formed in the baseboard 25 in accordance with each gap formed between each of thereflective liquid crystal panel assemblies 30R″, 30G″ and 30B″ for therespective color lights and the transmission type polarizing plate 37for each color light secured on each of the incidence surfaces 40 a to40 c of the three-color combination cross dichroic prism 40, and asecond fan hole 25 d is formed in the base board 25 to face a heat sink33 b attached on a rear surface of the reflective liquid crystal panel33 for each color light.

Furthermore, an air stream W generated when rotating the fan 26 issupplied to an upper surface 25 a side of the base board 25 through thefirst and second fan holes 25 c and 25 d formed in the base board 25from a lower surface 25 b side of the base board 25. Here, the airstream W which has passed through the first fan hole 25 c is supplied toeach gap formed between the transparent glass plate 36 attached on thetriangular prismatic housing 31 for each color light and thetransmission type polarizing plate 37 for each color light secured oneach of the incidence surfaces 40 a to 40 c of the three-colorcombination cross dichroic prism 40 to cool a surface of the transparentglass plate 36 for each color light and the transmission type polarizingplate 37 for each color light secured on each of the incidence surfaces40 a to 40 c of the three-color combination cross dichroic prism 40, andthe air stream W which has passed through the second fan hole 25 d coolsthe heat sink 33 b attached on the rear surface of the reflective liquidcrystal panel 33 for each color light. Therefore, it is possible tosuppress an increase in temperatures of the reflective liquid crystalpanel 33 for each color light, the transparent glass plate 36 for eachcolor light and the transmission type polarizing plate 37 for each colorlight secured on each of the incidence surfaces 40 a to 40 c of thethree-color combination cross dichroic prism 40 to avoid deteriorationdue to heat generation, and high luminance and high contrast can bethereby achieved, which contributes to an improvement in reliabilitywith respect to the projection type display apparatus 10B ofModification 2 obtained by partially modifying Embodiment 1.

A projection type display apparatus 10C of Modification 3 obtained bypartially modifying the projection type display apparatus 10 ofEmbodiment 1 will now be briefly described while mainly focusing on adifference from Embodiment 1 (FIGS. 4, 5A and 5B) with reference toFIGS. 12, 13A and 13B.

FIG. 12 is a plan view showing a configuration of the projection typedisplay apparatus of Modification 3 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention. FIGS. 13A and 13B are a perspective view showingrespective reflective liquid crystal panel assemblies for R, G and Blights and a three-color combination cross dichroic prism and a sideview showing the reflective liquid crystal panel assembly for the Blight, the three-color combination cross dichroic prism and thereflective liquid crystal panel assembly for the R light in Modification3 obtained by partially modifying the projection type display apparatusof Embodiment 1.

As shown in FIGS. 12, 13A and 13B, a projection type display apparatus10C of Modification 3 obtained by partially modifying Embodiment 1 hasthe following characteristics. That is, a technical concept ofModification 2 of Embodiment 1 is applied to a reflective liquid crystalpanel assembly 30R″ for R light and a reflective liquid crystal panelassembly 30G″ for G light, and a transmission type polarizing plate 37which is of a light absorption type as unnecessary polarized lightremoving means for the R light and the G light is secured on each ofincidence surfaces 40 a and 40 b of a three-color combination crossdichroic prism 40. On the other hand, a technical concept ofModification 1 of Embodiment 1 is applied to a reflective liquid crystalpanel assembly 30B′ for B light, and a reflective polarizing plate 35relatively having heat resisting properties and light stability is usedas unnecessary polarized light removing means for the B light in thereflective liquid crystal panel assembly 30B′ for the B light.

That is, in Modification 3 of Embodiment 1, each of the reflectiveliquid crystal panel assembly 30R″ for R light, the reflective liquidcrystal panel assembly 30G″ for G light and the reflective liquidcrystal panel assembly 30B′ for B light has the following configuration.That is, a hollow triangular prismatic housing 31 is first prepared foreach light and, in the triangular prismatic housing 31 for each colorlight, a tabular reflective polarizing plate (a so-called “wire gridpolarizer”) 32 as polarization splitting means is attached on a firstsurface 31 a (FIG. 6) having an inclination angle of approximately 45°with respect to an optical axis of each color light from each colorlight illuminating means from a light source 11 to color separationoptical systems 17 and 19, and a reflective liquid crystal panel 33 foreach color light is attached on a second surface 31 b (FIG. 6)orthogonal to the optical axis of each color light transmitted throughthe reflective polarizing plate 32 for each color. This point is thesame as Embodiment 1. However, the following points are different fromEmbodiment 1. That is, a transparent glass plate 36 for the R light orthe G light is attached on a third surface 31 c orthogonal to theoptical axis of the R light or the G light obtained by reflectingreflected light from the reflective liquid crystal panel 33 for the Rlight or the G light by the reflective polarizing plate 32 for the Rlight or the G light in place of the transmission type polarizing plate34 (FIGS. 4, 5A and 5B) of Embodiment 1, a reflective polarizing plate35 for the B light as unnecessary polarized light removing means isattached on the third surface 31 c (FIG. 6) orthogonal to the opticalaxis of the B light obtained by reflecting reflected light from thereflective liquid crystal panel 33 for the B light by the reflectivepolarizing plate 32 for the B light in place of the transmission typepolarizing plate 34 (FIGS. 4, 5A and 5B) of Embodiment 1, and a side onwhich the transparent glass plate 36 for the R light or the G light isarranged faces a transmission type polarizing plate 37 as unnecessarypolarized light removing means for the R light or the G light secured oneach of incidence surfaces 40 a and 40 b of a three-color combinationcross dichroic prism 40 with each gap therebetween, and a side on whichthe reflective polarizing plate 35 for the B light is arranged faces anincidence surface 40 c of the three-color combination cross dichroicprism 40 with a gap therebetween.

Although the wire grip polarizer is used as the reflective polarizingplate 35 with respect to the G light only in Modification 3 ofEmbodiment 1, a cost per wire grid polarizing is generally expensive ascompared with that of the transmission type polarizing plate 37 which isof a light absorption type. Further, since the reflective polarizingplate 35 reflects unnecessary polarized light, there is a problem thatthe reflected unnecessary polarized light again returns to thereflective liquid crystal panel 33 and further returns to a projectionlens 42 side to project an unwanted component onto a non-illustratedscreen or unnecessary polarized light reflected from a surface of theprojection lens 42 or the like returns to the projection lens 42 by thereflective polarizing plate 35 to be projected onto the screen as aghost image.

Therefore, considering balance with a cost and reliability, thetransmission type polarizing plate 37 which is of a light absorptiontype is used with respect to the R light and the G light, and thereflective polarizing plate 35 relatively having heat resistingproperties and light stability is used with respect to the B light. Inthis example, the reflective polarizing plate 35 is used with respect tothe B light because the transmission type polarizing plate 37 which isof the light absorption type has a high light absorption ratio on ashort wavelength side and great heat generation and polarizationcharacteristics of the B light tends to be lowered due to weak lightstability with respect to the B light having a short wavelength, wherebyan improvement with respect to the B light is effective as compared withthe R light or the G light.

Furthermore, in Modification 3 of Embodiment 1, when the transmissiontype polarizing plate 37 for the R light or the G light and thereflective type polarizing plate 35 for the B light are air-cooled byusing a fan 26, it is likewise possible to suppress an increase intemperatures of the reflective liquid crystal panel 33, the reflectivepolarizing plate 35, the transparent glass plate 36 and the transmissiontype polarizing plate 37 to avoid deterioration due to heat generation,and hence high luminance and high contrast can be achieved, whichcontributes to an improvement in reliability with respect to theprojection type display apparatus 10C of Modification 3.

A projection type display apparatus 10D of Modification 4 obtained bypartially modifying the projection type display apparatus 10 ofEmbodiment 1 will now be briefly described while mainly focusing on adifference from Embodiment 1 (FIGS. 4, 5A and 5B) with reference toFIGS. 14, 15A and 15B.

FIG. 14 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 4 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention. FIGS. 15A and 15B is a perspective view showingrespective reflective liquid crystal panel assemblies for R, G and Blight and a three-color combination cross dichroic prism and a side viewshowing the reflective liquid crystal panel assembly for the B light,the three-color combination cross dichroic prism and the reflectiveliquid crystal panel assembly for the R light in Modification 4 obtainedby partially modifying the projection type display apparatus ofEmbodiment 1.

As shown in FIGS. 14, 15A and 15B, in a projection type displayapparatus 10D of Modification 4 obtained by partially modifyingEmbodiment 1, like Modification 3 of Embodiment 1, a technical conceptof Modification 2 of Embodiment 1 is applied to a reflective liquidcrystal panel assembly 30R″ for R light and a reflective liquid crystalpanel assembly 30G″ for G light, and a transmission type polarizingplate 37 which is of a light absorption type as unnecessary polarizedlight removing means for the R light or the G light is secured on eachof incidence surfaces 40 a and 40 b of a three-color combination crossdichroic prism 40. On the other hand, a technical concept ofModification 1 of Embodiment 1 is applied to a reflective liquid crystalpanel assembly 30B′ for B light, and a reflective polarizing plate 35relatively having heat resisting properties and light stability asunnecessary polarized light removing means for the B light is used inthe reflective liquid crystal panel assembly 30B′ for the B light. Thisis the same configuration as Modification 3 of Embodiment 1. However, anonly difference from Modification 3 of Embodiment 1 lies in that thereflective polarizing plate 35 for the B light in the reflective liquidcrystal panel assembly 30B′ for the B light is directly secured on anincidence surface 40 c of the three-color combination cross dichroicprism 40.

In this example, the reflective liquid crystal panel assembly 30B′ forthe B light is formed into a trapezoidal prism 43 in place of thetriangular prismatic housing 31 in such a manner that the same opticalpath length as those of the reflective liquid crystal panel assembly30R″ for the R light and the reflective liquid crystal panel assembly30G″ for the G light can be obtained with respect to the three-colorcombination cross dichroic prism 40, and a reflective polarizing plate32, a reflective liquid crystal panel 33 and the reflective polarizingplate 35 are accommodated in the trapezoidal prism 43 for the B lightwith the inside of the prism being sealed as shown in the drawing.

Therefore, the projection type display apparatus 10D of Modification 4obtained by partially modifying Embodiment 1 can acquire substantiallythe same advantages as those of the projection type display apparatus10C of Modification 3 of Embodiment 1.

A projection type display apparatus 10E of Modification 5 obtained bypartially modifying the projection type display apparatus 10 ofEmbodiment 1 will now be briefly described while mainly focusing on adifference from Embodiment 1 (FIGS. 4, 5A and 5B) with reference toFIGS. 16, 17A and 17B.

FIG. 16 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 5 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention. FIGS. 17A and 17B are a perspective view showingrespective reflective liquid crystal panel assemblies for R, G and Blights and a three-color combination cross dichroic prism and a sideview showing the reflective liquid crystal panel assembly for the Blight, the three-color combination cross dichroic prism and thereflective type liquid crystal panel assembly for the R light inModification 5 obtained by partially modifying the projection typedisplay apparatus of Embodiment 1.

As shown in FIGS. 16, 17A and 17B, in a projection type displayapparatus 10E of Modification 5 obtained by partially modifyingEmbodiment 1, a technical concept of Embodiment 1 is applied to areflective liquid crystal panel assembly 30R for R light and areflective liquid crystal panel assembly 30G for G light, and atransmission type polarizing plate 34 which is of a light absorptiontype as unnecessary polarized light removing means for the R light orthe G light is used in each of the reflective liquid crystal panelassemblies 30R and 30G for the R light and the G light. On the otherhand, a technical concept of Modification 1 of Embodiment 1 is appliedto a reflective liquid crystal panel assembly 30B′ for B light, and areflective polarizing plate 35 relatively having heat resistingproperties and light stability as unnecessary polarized light removingmeans for the B light is used in the reflective liquid crystal panelassembly 30B′ for the B light. However, this modification ischaracterized in that the reflective liquid crystal panel assembly 30Rfor the R light, the reflective liquid crystal panel assembly 30G forthe G light and the reflective liquid crystal panel assembly 30B′ forthe B light are appressed against respective incidence surfaces 40 a to40 c of the three-color combination cross dichroic prism 40 without gap.

In this example, with each of the incidence surfaces 40 a to 40 c of thethree-color combination cross dichroic prism 40 being determined as oneside, the inside a triangular prismatic housing 31 for each color lightis sealed, and the transmission type polarizing plates 34 for the Rlight and the G light and the reflective polarizing plate 35 for the Blight are appressed against the respective incidence surfaces 40 a to 40c of the three-color combination cross dichroic prism 40 without gap. Asa result, even if air-cooling between these members is eliminated, heatgeneration is small when power of a light source 11 is relatively small.Therefore, heat from the light source 11 can escape to the inside of thethree-color combination cross dichroic prism 40. Accordingly, a fan doesnot have to be provided on a lower surface 25 b side of a base board 25,but providing the fan 26 as required can cool a rear surface of thereflective liquid crystal panel 33 for each color light.

Moreover, when the reflective liquid crystal panel assembly 30R for theR light, the reflective liquid crystal panel assembly 30G for the Glight and the reflective liquid crystal panel assembly 30B′ for the Blight are appressed against the respective incidence surfaces 40 a to 40c of the three-color combination cross dichroic prism 40, colorseparation and color combination optical systems can be reduced in size.Additionally, since a transparent glass plate 36 is not attached in thetriangular prismatic housing 31 for each color light, unwanted reflectedlight by interface reflection from the transparent glass plate 36 is notgenerated.

It is to be noted that the description has been given as to the examplewhere the absorption type polarizing plates are used for the R and Glights and the reflective polarizing plate is used for the B light asthe unnecessary polarized light removing means for each color light inModifications 3 to 5 of Embodiment 1 mentioned above, but the presentinvention is not restricted thereto, and the absorption type polarizingplate may be used for the R light and the reflective polarizing platesmay be used for the G and B lights. In this case, when power of thelight source (a lamp) is increased in order to improve brightness,reliability of a G light band can be also enhanced.

A projection type display apparatus 10F of Modification 6 obtained bypartially modifying the projection type display apparatus 10 ofEmbodiment 1 will now be briefly described while mainly focusing on adifference from Embodiment 1 (FIGS. 4, 5A and 5B) with reference toFIGS. 18, 19A, 19B and 20.

FIG. 18 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 6 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention. FIGS. 19A and 19B are a perspective view showingrespective reflective liquid crystal panel assemblies for R, G and Blights and a three-color combination cross dichroic prism and a sideview showing the three-color combination cross dichroic prism and thereflective liquid crystal panel assembly for the G light in Modification6 obtained by partially modifying the projection type display apparatusof Embodiment 1. FIG. 20 is a perspective view showing the reflectiveliquid crystal panel assembly for the R light, the G light or the Blight in an enlarging manner in Modification 6 obtained by partiallymodifying the projection type display apparatus of Embodiment 1.

As shown in FIGS. 18, 19A and 19B, in the projection type displayapparatus 10F of Modification 6 obtained by partially modifyingEmbodiment 1, a shape of a third surface 46 c (FIG. 20) in eachtriangular prismatic housing 46 is different from that of the triangularprismatic housing 31 (FIGS. 4, 5A and 5B) of Embodiment 1, eachtriangular prismatic housing 46 being provided in each of a reflectiveliquid crystal panel assembly 45R for R light, a reflective liquidcrystal panel assembly 45G for G light and a reflective liquid crystalpanel assembly 45B for B light.

That is, as shown in FIG. 20 in an enlarging manner, in Modification 6of Embodiment 1, each of the reflective liquid crystal panel assembly45R for the R light, the reflective liquid crystal panel assembly 45Gfor the G light and the reflective liquid crystal panel assembly 45B forthe B light has the following configuration. That is, a hollowtriangular prismatic housing 46 is first prepared for each color lightand, in the triangular prismatic housing 46 for each color light, atabular reflective polarizing plate 32 (a so-called “wire gridpolarizer”) as polarization splitting means is attached on a firstsurface 46 a having an inclination angle of approximately 45° withrespect to an optical axis of each color light from each color lightilluminating means from a light source 11 (FIG. 18) to color separationoptical systems 17 and 19 (FIG. 18), and a reflective liquid crystalpanel 33 is attached on a second surface 46 b orthogonal to the opticalaxis of each color light transmitted through the reflective polarizingplate 32 for each color light. This point is the same as Embodiment 1.However, a transmission type polarizing plate 34 as unnecessarypolarized light removing means is attached on a third surface 46 chaving a predetermined inclination angle θ with respect to the opticalaxis of each color light obtained by reflecting reflected light from thereflective liquid crystal panel 33 for each color light by thereflective polarizing plate 32 for each color light, and unnecessaryreflected light from a projection lens 42 side is prevented from beingprojected by the transmission type polarizing plate 34 for each colorlight which is inclined at a predetermined angle. Furthermore, in astate where a space of the triangular prismatic housing 46 surrounded bythe first surface 46 a to the third surface 46 c is sealed from dust orthe like by a lower surface 46 d and an upper surface 46 e, each side onwhich the transmission type polarizing plate 34 for each color light isarranged faces each of the incidence surfaces 40 a to 40 c (FIGS. 18,19A and 19B) of the three-color cross dichroic prism 40 with each gaptherebetween.

In this example, as to an inclination direction of the third surface 46c as a light emission surface side of the triangular prismatic housing46, it is desirable to incline the third surface 46 c along spread oflight emitted from the liquid crystal panel 33 for each color light.Additionally, the inclination angle θ of the third surface 46 c of thetriangular prismatic housing 46 is set as an angle formed by a normalline of the transmission type polarizing plate 34 for each color lightattached along this third surface 46 c and the optical axis of eachcolor light, and it is effective to incline the third surface 46 c insuch a manner that a light ray having a maximum angle of an effectivelight beam of each color light emitted from the liquid crystal panel 33for each color light exceeds a fetch angle of the projection lens 42(FIG. 18). Specifically, the third surface 46 c of the triangularprismatic housing 46 is inclined so that the inclination angle θ becomes10° or above when the projection lens 42 of F2.8 is used, and the sameis inclined so that the inclination angle θ becomes approximately 8°when the projection lens 42 of F3.2 is used.

It is to be noted that the triangular prismatic housing 46 is likewiseapplied to later-described Modifications 7 to 9 obtained by partiallymodifying Embodiment 1.

Here, giving a description on the unnecessary reflected light from theprojection lens 42 side, an AR coat (Anti Reflection Coat) is applied oneach interface of each optical component from the transmissionpolarizing plate 34 for each color light to the projection lens 42, andan interface reflection loss generated on each interface of each opticalcomponent is reduced as much as possible. However, even if the AR coatis applied on each interface of each optical component, reflection ofapproximately 0.2% to 1% occurs to generate unnecessary reflected light.Additionally, when this unnecessary reflected light is projected onto ascreen (not shown) through the projection lens 42, contrast ofcolor-combined image light emitted from the projection lens 42 islowered, or a ghost image is displayed.

Accordingly, in the projection type display apparatus 10F ofModification 6 obtained by partially modifying Embodiment 1, the thirdsurface 46 c as the light emission surface side of the triangularprismatic housing 46 for each color light is inclined at a predeterminedangle with respect to an optical axis of each color light, and thetransmission type polarizing plate 34 for each color light is obliquelyattached along this third surface 46 c. As a result, when theunnecessary reflected light from the projection lens 42 side returns tothe transmission type polarizing plate 34 for each color light and theunnecessary reflected light again enters the projection lens 42 throughthe three-color combination cross dichroic prism 40 by interfacereflection of the transmission type polarizing plate 34 for each colorlight, the unnecessary reflected light deviates from the fetch angle ofthe projection lens 42, whereby the unnecessary reflected light does notreach the screen (not shown).

As a result, contrast is not lowered with respect to color-combinedimage light emitted from the projection lens 42, and a factor ofdisplaying a ghost image can be also eliminated. Therefore, thecolor-combined image light with high picture quality can be projectedonto the screen.

Further, color purity can be increased by adding an unnecessarywavelength band restricting effect to the transmission type polarizingplate 34 for each color light attached on the third surface 46 c of thetriangular prismatic housing 46.

Furthermore, it is possible to eliminate a ghost component which entersthe liquid crystal panel 33 for a given color from the liquid crystalpanel 33 for another color. For example, a mixed-color component betweenthe respective R, G and B bands can be attenuated by adopting thetransmission type polarizing plate 34 for each color light on which adichroic filter with reduced bandwidths of R, G and B is deposited. Ofcourse, since the transmission type polarizing plate 34 for each colorlight having the dichroic filter is inclined at a predetermined anglewith respect to the optical axis of each color light as described above,unwanted reflected light from the projection lens 42 side does not reachthe screen (not shown) even if a reflective wavelength band restrictingfunction of a dichroic film or the like is provided, thereby obtaining aprojected image with high color purity and high contrast.

Moreover, in Modification 6 of Embodiment 1, as shown in FIGS. 19A and19B, since an air stream W generated when rotating a fan 26 is suppliedto an upper surface 25 a side of a base board 25 from a lower surface 25b side of the base board 25 through first and second fan holes 25 c and25 d formed in the base board 25, it is possible to suppress an increasein temperatures of the reflective liquid crystal panel 33 for each colorlight, the transmission type polarizing plate 34 for each color lightand the three-color combination cross dichroic prism 40 by air-coolingof the fan 26 to further assuredly avoid deterioration due to heatgeneration, whereby high luminance and high contrast can be achieved,which contributes to an improvement in reliability with respect to theprojection type display apparatus 10F of Modification 6.

A projection type display apparatus 10G of Modification 7 obtained bypartially modifying the projection type display apparatus 10 ofEmbodiment 1 will now be briefly described while mainly focusing on adifference from Embodiment 1 (FIGS. 4, 5A and 5B) and Modification 1(FIGS. 8, 9A and 9B) obtained by partially modifying Embodiment 1 withreference to FIGS. 21, 22A and 22B.

FIG. 21 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 7 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention. FIGS. 22A and 22B are a perspective view showingrespective reflective liquid crystal panel assemblies for R, G and Blights and a three-color combination cross dichroic prism and a sideview showing the three-color combination cross dichroic prism and thereflective liquid crystal panel assembly for the G light in Modification7 obtained by partially modifying the projection type display apparatusof Embodiment 1.

As shown in FIGS. 21, 22A and 22B, in a projection type displayapparatus 10G of Modification 7 obtained by partially modifyingEmbodiment 1, a shape of a third surface 46 c (FIG. 20) of a triangularprismatic housing 46 provided in each of a reflective liquid crystalpanel assembly 45R′ for R light, a reflective liquid crystal panelassembly 45G′ for G light and a reflective liquid crystal panel assembly45B′ for B light is different from those of the triangular prismatichousing 31 (FIGS. 4, 5A and 5B) of Embodiment 1 and the triangularprismatic housing 31 (FIGS. 8, 9A and 9B) of Modification 1. On theother hand, a reflective polarizing plate 35 for each color light whichreflects unnecessary polarized light as unnecessary polarized lightremoving means is provided on this third surface 46 c, which is the sameas Modification 1.

That is, in Modification 7 of Embodiment 1, each of the reflectiveliquid crystal panel assembly 45R′ for the R light, the reflectiveliquid crystal panel assembly 45G′ for the G light and the reflectiveliquid crystal panel assembly 45B′ for the B light has the followingconfiguration. That is, a hollow triangular prismatic housing 46 isfirst prepared for each color light and, in the triangular prismatichousing 46 for each color light, a tabular reflective polarizing plate32 (a so-called “wire grid polarizer”) as polarization splitting meansis attached on a first surface 46 a (FIG. 20) having an inclinationangle of approximately 45° with respect to an optical axis of each colorlight from each color light illuminating means from a light source 11 tocolor separation optical systems 17 and 19, and a reflective liquidcrystal panel 33 is attached on a second surface 46 b (FIG. 20)orthogonal to the optical axis of each color light transmitted throughthe reflective polarizing plate 32 for each color light. This point isthe same as Embodiment 1 and Modification 1. However, a difference fromEmbodiment 1 and Modification 1 lies in that a reflective polarizingplate 35 as unnecessary polarized light removing means is attached on athird surface 46 c (FIG. 20) having a predetermined inclination angle θ(FIG. 20) with respect to the optical axis of each color light obtainedby reflecting reflected light from the reflective liquid crystal panel33 for each color light by the reflective polarizing plate 32 for eachcolor light in place of the transmission type polarizing plate 34 ofEmbodiment 1 (FIGS. 4, 5A and 5B) so that unnecessary reflected lightfrom a projection lens 42 side is prevented from being projected by thereflective type polarizing plate 35 for each color light inclined at apredetermined angle, and each side on which the reflective polarizingplate 35 for each color light is arranged faces each of incidencesurfaces 40 a to 40 c of a three-color combination cross dichroic prism40 with a gap therebetween.

In this example, the inclination angle θ (FIG. 20) of the third surface46 c as a light emission surface side of the triangular prismatichousing 46 is set as an angle formed by a normal line of the reflectivepolarizing plate 35 for each color light attached along this thirdsurface 46 c and the optical axis of each color light, and it iseffective to incline the third surface 46 c in such a manner that alight ray having a maximum angle of an effective light beam of eachcolor light emitted from the liquid crystal panel 33 for each colorlight exceeds a fetch angle of the projection lens 42 (FIG. 21).Specifically, the third surface 46 c is inclined so that the inclinationangle θ becomes 10° or above when the projection lens 42 of F2.8 isused, and the same is inclined so that the inclination angle θ becomesapproximately 8° when the projection lens 42 of F3.2 is used.

Therefore, in the projection type display apparatus 10G of Modification7 obtained by partially modifying Embodiment 1, the third surface 46 cas the light emission surface side of the triangular prismatic housing46 for each color light is inclined at a predetermined angle withrespect to the optical axis of each color light, and the reflectivepolarizing plate 35 for each color light is obliquely attached alongthis third surface 46 c. As a result, when unnecessary reflected lightfrom the projection lens 42 side returns to the reflective polarizingplate 35 for each color light and the unnecessary reflected light againenters the projection lens 42 through the three-color combination crossdichroic prism 40 by interface reflection of the reflective polarizingplate 35 for each color light, the unnecessary reflected light deviatesfrom the fetch angle of the projection lens 42 so that it does not reacha screen (not shown).

As a result, contrast is not lowered with respect to color-combinedimage light emitted from the projection lens 42, and a factor ofdisplaying a ghost image is also eliminated. Therefore, thecolor-combined image light with high picture quality can be projectedonto the screen.

Moreover, for example, when a dichroic filter with reduced bandwidths ofR, G and B is deposited on the reflective polarizing plate 35 for eachcolor light attached on the third surface 46 c of the triangularprismatic housing 46 to add an unnecessary wavelength band restrictingeffect, it is possible to obtain a projected image having high colorpurity and improved contrast.

Additionally, in Modification 7 of Embodiment 1, as shown in FIGS. 22Aand 22B, likewise, since an air stream W generated when rotating a fan26 is supplied to an upper surface 25 a side of a base board 25 from alower surface 25 b side of the base board 25 through first and secondfan holes 25 c and 25 d formed in the base board 25, it is possible tosuppress an increase in temperatures of the reflective liquid crystalpanel 33 for each color light, the reflective polarizing plate 35 foreach color light and the three-color combination cross dichroic prism 40by air-cooling of the fan 26 to further assuredly avoid deteriorationdue to heat generation, whereby high luminance and high contrast can beachieved, which contributes to an improvement in reliability withrespect to the projection type display apparatus 10G of Modification 7.

A projection type display apparatus 10H of Modification 8 obtained bypartially modifying the projection type display apparatus 10 ofEmbodiment 1 will now be briefly described while mainly focusing on adifference from Embodiment 1 (FIGS. 4, 5A and 5B) and Modification 2(FIGS. 10, 11A and 11B) obtained by partially modifying Embodiment 1with reference to FIGS. 23, 24A and 24B.

FIG. 23 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 8 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention. FIGS. 24A and 24B are a perspective view showingrespective reflective liquid crystal panel assemblies for R, G and Blights and a three-color combination cross dichroic prism and a sideview showing the three-color combination cross dichroic prism and thereflective liquid crystal panel assembly for the G light in Modification8 obtained by partially modifying the projection type display apparatusof Embodiment 1.

As shown in FIGS. 23, 24A and 24B, in the projection type displayapparatus 10H of Modification 8 obtained by partially modifyingEmbodiment 1, a shape of a third surface 46 (FIG. 20) of each triangularprismatic housing 46 provided in a reflective liquid crystal panelassembly 45R″ for R light, a reflective liquid crystal panel assembly45G″ for G light and a reflective liquid crystal panel assembly 45B″ forB light is different from those of the triangular prismatic housing 31(FIGS. 4, 5A and 5B) of Embodiment 1 and the triangular prismatichousing 31 (FIGS. 10, 11A and 11B) of Modification 2. On the other hand,a transparent glass plate 36 for each color light is attached on thisthird surface 46 c, and a transmission type polarizing plate 37 which isof a light absorption type as unnecessary polarized light removing meansfor each color light is secured on each of incidence surfaces 40 a to 40c of a three-color combination cross dichroic prism 40 in such a mannerthat this transmission type polarizing plate 37 faces the transparentglass plate 36 for each color light. These points are the same asModification 2.

That is, in Modification 8 of Embodiment 1, each of the reflectiveliquid crystal panel assembly 45R″ for the R light, the reflectiveliquid crystal panel assembly 45G″ for the G light and the reflectiveliquid crystal panel assembly 45B″ for the B light has the followingconfiguration. That is, a hollow triangular prismatic housing 46 isfirst prepared for each color light and, in the triangular prismatichousing 46 for each color light, a tabular reflective polarizing plate(a so-called “wire grid polarizer”) 32 as polarization splitting meansis attached on a first surface 46 a having an inclination angle ofapproximately 45° with respect to an optical axis of each color lightfrom each color light illuminating means from a light source 11 to colorseparation optical systems 17 and 19, and a reflective liquid crystalpanel 33 is attached on a second surface 46 b (FIG. 20) orthogonal tothe optical axis of each color light transmitted through the reflectivepolarizing plate 32 for each color light. This point is the same asEmbodiment 1 and Modification 2. However, a difference from Embodiment 1and Modification 2 lies in that the transparent glass plate 36 isattached on the third surface 46 c (FIG. 20) having a predeterminedinclination angle θ (FIG. 20) with respect to the optical axis of eachcolor light obtained by reflecting reflected light from the reflectiveliquid crystal panel 33 for each color light by the reflectivepolarizing plate 32 for each color light in place of the transmissiontype polarizing plate 34 (FIGS. 4, 5A and 5B) of Embodiment 1 in orderto prevent unnecessary reflected light from a projection lens 42 sidefrom being projected by the transparent glass plate 36 for each colorlight inclined at a predetermined angle, and each side on which thetransparent glass plate 36 for each color light is arranged faces eachof incidence surfaces 40 a to 40 c of the three-color combination crossdichroic prism 40 with a gap therebetween.

Based on the above-described configuration, the transmission typepolarizing plate 37 which is of a light absorption type as unnecessarypolarized light removing means for each color light which removesunnecessary polarized light from each color light transmitted throughthe transparent glass plate 36 for each color light is secured on eachof the incidence surfaces 40 a to 40 c of the three-color combinationcross dichroic prism 40. This point is the same as Modification 2.

In this example, the inclination angle θ (FIG. 20) of the third surface46 c as a light emission surface side of the triangular prismatichousing 46 is set as an angle formed by a normal line of the transparentglass plate 36 for each color light attached along this third surface 46c and an optical axis of each color light, and it is effective toincline the this surface 46 c in such a manner that a light ray with amaximum angle of an effective light beam of each color light emittedfrom the liquid crystal panel 33 for each color light exceeds a fetchangle of the projection lens 42 (FIG. 23). Specifically, the thirdsurface 46 c of the triangular prismatic housing 46 is inclined in sucha manner that the inclination angle θ becomes 10° or above when theprojection lens 42 of F2.8 is used, and the same is inclined in such amanner that the inclination angle θ becomes approximately 8° when theprojection lens 42 of F3.2 is used.

Therefore, in the projection type display apparatus 10H of Modification8 obtained by partially modifying Embodiment 1, the third surface 46 cas the light emission surface side of the triangular prismatic housing46 for each color light is inclined at a predetermined angle withrespect to the optical axis, and the transparent glass plate 36 isobliquely attached along this third surface 46 c. As a result, whenunnecessary reflected light from the projection lens 42 side returns tothe transparent glass plate 36 for each color light and again enters theprojection lens 42 through the transmission type polarizing plate 37 foreach color light and the three-color combination cross dichroic prism 40by interface reflection of the transparent glass plate 36 for each colorlight, the unnecessary reflected light deviates from the fetch angle ofthe projection lens 42 so that it does not reach the screen (not shown).

Consequently, contrast is not lowered with respect to color-combinedimage light emitted from the projection lens 42 and a factor ofdisplaying a ghost image is also eliminated, thereby projecting thecolor-combined image light with high picture quality onto the screen.

Furthermore, for example, when a dichroic filter with narrowed bands ofR, G and B is deposited on the transparent glass plate 36 for each colorlight attached on the third surface 46 c of the triangular prismatichousing 46 to add an unnecessary wavelength band restricting effect,thereby obtaining a projected image with high color purity and highcontrast.

Moreover, in Modification 8 of Embodiment 1, as shown in FIGS. 24A and24B, an air stream W generated when rotating a fan 26 is supplied to anupper surface 25 a side of a base board 25 from a lower surface 25 bside of the base board 25 through first and second fan holes 25 c and 25d formed in this base board 25. Therefore, it is possible to suppress anincrease in temperatures of the reflective liquid crystal panel 33 foreach color light, the transparent glass plate 36 for each color lightand the transmission type polarizing plate 37 for each color lightsecured on each of the incidence surfaces 40 a to 40 c of thethree-color combination cross dichroic prism 40 to avoid deteriorationdue to heat generation. As a result, high luminance and high contrastcan be achieved, which contributes to an improvement in reliability withrespect to the projection type display apparatus 10H of Modification 8obtained by partially modifying Embodiment 1.

A projection type display apparatus 10I of Modification 9 obtained bypartially modifying the projection type display apparatus 10 ofEmbodiment 1 will now be briefly described while mainly focusing on adifference from Embodiment 1 (FIGS. 4, 5A and 5B) and Modification 3(FIGS. 12, 13A and 13B) obtained by partially modifying Embodiment 1with reference to FIGS. 25, 26A and 26B.

FIG. 25 is a plan view showing a configuration of a projection typedisplay apparatus of Modification 9 obtained by partially modifying theprojection type display apparatus of Embodiment 1 according to thepresent invention. FIGS. 26A and 26B are a perspective view showingrespective reflective liquid crystal panel assemblies for R, G and Blights and a three-color combination cross dichroic prism and a sideview showing the reflective liquid crystal panel assembly for the Blight, the three-color combination cross dichroic prism and thereflective liquid crystal panel assembly for the R light in Modification9 obtained by partially modifying the projection type display apparatusof Embodiment 1.

As shown in FIGS. 25, 26A and 26B, in the projection type displayapparatus 10I of Modification 9 obtained by partially modifyingEmbodiment 1, a shape of a third surface 46 c (FIG. 20) of a triangularprismatic housing 46 provided in each of a reflective liquid crystalpanel assembly 45R″ for R light, a reflective liquid crystal panelassembly 45G″ for G light and a reflective liquid crystal panel assembly45B′ for B light is different from those of the triangular prismatichousing 31 (FIGS. 4, 5A and 5B) of Embodiment 1 and the triangularprismatic housing 31 (FIGS. 12, 13A and 13B) of Modification 3. On theother hand, transparent glass plates 36 for the R light and G light arerespectively provided on the third surfaces 46 c of the respectivetriangular prismatic housings 46 for the R light and the G light, areflective polarizing plate 35 as unnecessary polarized light removingmeans with respect to the B light is attached on the third surface 46 cof the triangular prismatic housing 46 for the B light, and atransmission type polarizing plate 37 which is of a light absorptiontype as unnecessary polarized light removing means with respect to the Rlight and the G light is secured on each of incidence surfaces 40 a and40 b of a three-color combination cross dichroic prism 40. This point isthe same as Modification 3.

That is, in Modification 9 of Embodiment 1, each of the reflectiveliquid crystal panel assembly 45R″ for the R light, the reflectiveliquid crystal panel assembly 45G″ for the G light and the reflectiveliquid crystal panel assembly 45B′ for the B light has the followingconfiguration. That is, the hollow triangular prismatic housing 46 isfirst prepared for each color light and, in the triangular prismatichousing 46 for each color light, a tabular reflective polarizing plate(a so-called “wire grid polarizer”) 32 as polarization splitting meansis attached on a first surface 46 a (FIG. 20) having an inclinationangle of approximately 45° with respect to an optical axis of each colorlight from each color light illuminating means from a light source 11 tocolor separation optical systems 17 and 19, and a reflective liquidcrystal panel 33 for each color light is attached on a second surface 46b (FIG. 20) orthogonal to the optical axis of each color lighttransmitted through the reflective polarizing plate 32 for each colorlight. This point is the same as Embodiment 1 and Modification 3.However, each of the transparent glass plate 36 for the R light or the Glight is attached on the third surface 46 c (FIG. 20) having apredetermined inclination angle θ (FIG. 20) with respect to the opticalaxis of the R light or the G light obtained by reflecting each reflectedlight from the reflective liquid crystal panel 33 for the R light or theG light by the reflective polarizing plate 32 for the R light or the Glight in place of the transmission type polarizing plate 34 (FIGS. 4, 5Aand 5B) of Embodiment 1, and the reflective polarizing plate 35 for theB light as the unnecessary polarized light removing means is attached onthe third surface 46 c (FIG. 20) having the predetermined inclinationangle θ with respect to the optical axis of the B light obtained byreflecting reflected light from the reflective liquid crystal panel 33for the B light by the reflective polarizing plate 32 for the B light inplace of the transmission type polarizing plate 34 (FIGS. 4, 5A and 5B)of Embodiment 1. As a result, unnecessary reflected light from aprojection lens 42 side is prevented from being projected by thetransparent glass plates 36 for the R light and the G light and thereflective polarizing plate 35 for the B light inclined at thepredetermined angle. Moreover, a side on which the transparent glassplate 36 for the R light or the G light is arranged faces thetransmission type polarizing plate 37 as the unnecessary polarized lightremoving means for the R light or the G light secured on each of theincidence surfaces 40 a and 40 b of the three-color combination crossdichroic prism 40 with a gap therebetween, and a side on which thereflective polarizing plate 35 for the B light is arranged faces theincidence surface 40 c of the three-color combination cross dichroicprism 40 with a gap therebetween. This point is different fromEmbodiment 1 and Modification 3.

In this example, the inclination angle θ (FIG. 20) of the third surface46 c as a light emission surface side of the triangular prismatichousing 46 is set as an angle formed by each normal line of thetransparent glass plates 36 for the R light and the G light and thereflective polarizing plate 35 for the B light respectively attachedalong this third surface 46 c and an optical axis of each color light,and it is effective to incline the third surface 46 c in such a mannerthat a light ray having a maximum angle of an effective light beam ofeach color light emitted from the liquid crystal panel 33 for each colorlight exceeds a fetch angle of the projection lens 42 (FIG. 25).Specifically, the third surface 46 c of the triangular prismatic housing46 is inclined in such a manner that the inclination angle θ becomes 10°or above when the projection lens 42 of F2.8 is used, and the same isinclined in such a manner that the inclination angle θ becomesapproximately 8° when the projection lens 42 of F3.2 is used.

Therefore, in the projection type display apparatus 10I of Modification9 obtained by partially modifying Embodiment 1, the third surface 46 cas the light emission surface side of the triangular prismatic housing46 for each color light is inclined with respect to the optical axis ofeach color light at a predetermined angle, and each of the transparentglass plates 36 for the R light and the G light and the reflectivepolarizing plate 35 for the B light is obliquely attached along thisthird surface 46 c. As a result, when unnecessary reflected light fromthe projection lens 42 side returns to the transparent glass plates 36for the R light and the G light and the reflective polarizing plate 35for the B light and again enters the projection lens 42 through thetransmission type polarizing plates 37 for the R light and the G lightand the three-color combination cross dichroic prism 40 by eachinterface reflection of the transparent glass plates 36 for the R lightand the G light and the reflective polarizing plate 35 for the B light,the unnecessary reflected light deviates from the fetch angle of theprojection lens 42 so that it does not reach a screen (not shown).

As a result, contrast is not lowered with respect to color-combinedimage light emitted from the projection lens 42, and a factor ofdisplaying a ghost image can be also eliminated, thereby projecting thecolor-combined image light with high picture quality onto the screen.

Additionally, when dichroic filters with narrowed bands of R, G and Bare deposited on the transparent glass plates 36 for the R light and theG light and the reflective polarizing plate 35 for the B light attachedon the third surfaces 46 c of the triangular prismatic housings 46 toadd an unnecessary wavelength band restricting effect, a projected imagewith high color purity and high contrast can be obtained.

Further, in Modification 9 of Embodiment 1, as shown in FIGS. 26A and26B, an air stream W generated when rotating a fan 26 is supplied to anupper surface 25 a side of a base board 25 from a lower surface 25 bside of a base board 25 through first and second fan holes 25 c and 25 dformed in this base board 25. Therefore, it is possible to suppress anincrease in temperatures of the reflective liquid crystal panel 33, thereflective polarizing plate 35, the transparent glass plate 36 and thetransmission type polarizing plate 37 by air-cooling of the fan 26 toavoid heat generation. As a result, high luminance and high contrast canbe achieved, which contributes to an improvement in reliability withrespect to the projection type display apparatus 10I of Modification 9obtained by partially modifying Embodiment 1.

Embodiment 2

FIG. 27 is a plan view showing a configuration of a projection typedisplay apparatus of Embodiment 2 according to the present invention.FIG. 28 is a side view showing a three-color combination prism and areflective liquid crystal panel assembly for G light in the projectiontype display apparatus of Embodiment 2 according to the presentinvention.

As shown in FIG. 27, a projection type display apparatus 50 ofEmbodiment 2 according to the present invention is configured as areflective type which reflects light as a spatial light modulationelement corresponding to each of R light, G light and B light, but isdifferent from Embodiment 1 in a configuration of an optical system.

That is, in the projection type display apparatus 50 of Embodiment 2, onthe same plane are arranged a light source 51 which emits white light asnon-polarized light, color separation optical systems 58 and 60 whichsubjects the white light from the light source 51 to color separation toobtain the R light, the G light and the B light, respective spatiallight modulation elements (which will be referred to as reflectiveliquid crystal panels hereinafter) for the R, G and B lights, athree-color combination prism 90 which subjects image lights ofrespective colors which have been light-modulated by the respectiveliquid crystal panels 83 for the R, G and B lights to color combination,and a projection lens 92 which projects color-combined image lightobtained by this color combination prism 90.

First, the light source 51 emits white light as non-polarized lightincluding the R light, the G light and the B light by using a metalhalide lamp, a xenon lamp or a halogen lamp. The white light emittedfrom the light source 51 is reflected by a concave spherical reflectingmirror 52 to be turned to substantially parallel light, and this lightsequentially enters a first fly-eye lens array 53 attached on a frontsurface of the concave spherical reflecting mirror 52 and a secondfly-eye lens array 54 provided in front of this first fly-eye lens array53. These first and second fly-eye lens arrays 53 and 54 form a pair toconstitute an integrator which homogenizes an illumination distributionin a light beam of the white light. It is to be noted that anon-illustrated visible external light removing filter which cutsultraviolet light and infrared light may be arranged in front of thelight source 51.

Then, the white light as the non-polarized light whose illuminationdistribution has been homogenized by the first and second fly-eye lensarrays 53 and 54 enters a polarization converting prism array 55 as apolarization converting optical element. This polarization convertingprism array 55 has the same configuration as the polarization convertingprism array 15 (FIG. 4) of Embodiment 4, has a polarization splittingprism array and a λ/2 wave plate, and is entirely formed into a tabularshape. Further, the light transmitted through the polarizationconverting prism array 55 is turned to polarized light in apredetermined direction. In this Embodiment 2, like Embodiment 1, thepolarized light in a predetermined direction obtained by thepolarization converting prism array 55 is, e.g., P polarized light, butthe present invention is not restricted thereto, and it is possible toadopt a method which polarization-converts the white light from thelight source 51 into S polarized light by the light converting prismarray 55.

Thereafter, the white light as the P polarized light transmitted throughthe polarization converting prism array 55 is reflected by a first coldmirror 57 through a first field lens 56 so that its optical path isdeflected, and the light then enters a first dichroic mirror 58. Thisfirst dichroic mirror 58 transmits component lights of two colors out ofthree primary color lights therethrough and reflects the remaininglight. In this Embodiment 2, the first dichroic mirror 58 transmits theR light and the G light therethrough and reflects the B light, forexample.

Then, the R light and the G light transmitted through the first dichroicmirror 58 are reflected by a second cold mirror 59 and enter a seconddichroic mirror 60. This second dichroic mirror 60 transmits the R lighttherethrough and reflects the G light, for example.

Thereafter, the R light transmitted through the second dichroic mirror60 enters a reflective liquid crystal panel assembly 80R for R lightthrough a second field lens 61 and a polarizing plate 62.

On the other hand, the G light reflected by the second dichroic mirror60 enters a reflective liquid crystal panel assembly 80G for G lightthrough a third field lens 63 and a polarizing plate 64.

Further, the B light reflected by the first dichroic mirror 58 isreflected by a third cold mirror 65, further reflected by a fourth coldmirror 66 and enters a reflective liquid crystal panel assembly 80B forB light through a fourth field lens 67 and a polarizing plate 68.

The first and second dichroic mirrors 58 and 60 constitute each colorseparation optical system which subjects the white light from the lightsource 51 to color separation to obtain the R light, the G light and theB light, and the respective constituent members from the light source 51to the color separation optical systems 58 and 60 are respective colorlight illuminating means for illuminating the reflective liquid crystalpanels (reflective spatial light modulation elements) 83 for respectivecolor lights with the R light, the G light and the B light.

In the thus configured color separation optical systems, respectiveoptical path lengths from the light source 51 to the respective liquidcrystal panels 80R, 80G and 80B for the R, G and B lights aresubstantially equal to each other.

It is to be noted that the second to fourth cold mirrors 59, 65 and 66do not have to be cold mirrors, and they may be regular metal filmreflecting mirrors or dichroic mirrors which reflect respective colorlight bands as long as they have characteristics of reflecting incidentlights.

In this example, the reflective liquid crystal panel assembly 80R forthe R light, the reflective liquid crystal panel assembly 80G for the Glight and the reflective liquid crystal panel assembly 80B for the Blight all have the same configuration, and the reflective liquid crystalpanel assembly 80R for the R light, the reflective liquid crystal panelassembly 80G for the G light and the reflective liquid crystal panelassembly 80B for the B light face respective incidence surfaces of thethree-color combination prism 90 with respective gaps therebetween, thethree-color combination prism 90 being formed by bonding first to thirdprisms 90 a to 90 c as a color-combination optical system having adifferent shape from that of Embodiment 1.

Furthermore, the reflective liquid crystal panel assembly 80R for the Rlight, the reflective liquid crystal panel assembly 80G for the G light,the reflective liquid crystal panel assembly 80B for the B light and thethree-color combination prism 90 are fixed on an upper surface 70 a of abase board 70 (shown in FIG. 28 only) formed of an aluminum material orthe like by an adhesive.

Moreover, as shown in FIGS. 27 and 28, like Embodiment 1, each of thereflective liquid crystal panel assembly 80R for the R light, thereflective liquid crystal panel assembly 80G for the G light and thereflective liquid crystal panel assembly 80B for the B light has thefollowing configuration. That is, a hollow triangular prismatic housing81 (shown in FIG. 28 only) is first prepared for each color light and,in the triangular prismatic housing 81 for each color light, a tabularreflective polarizing plate (a sol-called “wire grid polarizer”) 82 aspolarization splitting means is attached on a first surface having aninclination angle of approximately 45° with respect to an optical axisof each color light from each color light illuminating means from thelight source 51 to the color separation optical systems 58 and 60, and areflective liquid crystal panel 83 is attached on a second surfaceorthogonal to the optical axis of each color light transmitted throughthe reflective polarizing plate 82 for each color light. Additionally, atransmission type polarizing plate 84 as unnecessary polarized lightremoving means is attached on a third surface orthogonal to the opticalaxis of each color light obtained by reflecting reflected light from thereflective liquid crystal panel 83 for each color light by thereflective polarizing plate 82 for each color light. Further, in a statewhere a space surrounded by the first to third surfaces of thetriangular prismatic housing 81 is sealed from dust or the like by alower surface and an upper surface, a side on which the transmissiontype polarizing plate 84 for each color light is arranged faces each ofincidence surfaces of the first to third prisms 90 a to 90 c of thethree-color combination prism 90 with a gap therebetween.

In this example, the reflective polarizing plate 82, the reflectiveliquid crystal panel 83 and the transmission type polarizing plate 84respectively attached and arranged on the triangular prismatic housing81 for each color light are vertically provided with respect to theupper surface 70 a of the base board 70 (shown in FIG. 28 only).Furthermore, a wave plate 83 a (shown in FIG. 28 only) which correctsthe liquid crystal corresponding to a pre-tilt by reciprocation isattached on a front surface of the reflective liquid crystal panel 83for each color light, and a heat sink 83 (shown in FIG. 28 only) whichcools the reflective liquid crystal panel 83 for each color light isattached on a rear surface of the reflective liquid crystal panel 83.

Moreover, when the R light, the G light and the B light of the Ppolarized components respectively enter the reflective liquid crystalpanel assembly 80R for the R light, the reflective liquid crystal panelassembly 80G for the G light and the reflective liquid crystal panelassembly 80B for the B light, the P polarized components only aretransmitted through the reflective polarizing plate 82 for each colorlight attached on the triangular prismatic housing 81 for each colorlight to enter the reflective liquid crystal panel 83 for each colorlight.

Then, each light beam light-modulated and reflected in accordance withan image signal of each color of the R light, the G light or the B lightin the reflective liquid crystal panel 83 for each color light returnsto the reflective polarizing plate 82 for each color light. Here, thereflective polarizing plate 82 for each color light subjects each lightbeam light-modulated and reflected by the reflective liquid crystalpanel 83 for each color light to polarization split, and the light beamwhose a linear polarized component in the other direction (an Spolarized component in this example) alone is reflected is transmittedthrough the transmission type polarizing plate 84 for each color light,and then enters the three-color combination prism 90 from threedirections.

In this example, the three-color combination prism 90 is a so-called“Phillips type prism”, and it is a prism which does not have a bondedportion at a part corresponding to a screen as described in, e.g.,Japanese Patent No. 2505758. This prism is used as a color separationprism in a so-called “three-panel type video camera”. This three-colorcombination prism 90 comprises at least first to third prisms 90 a to 90c arranged to form at least two sets of opposed surfaces. A firstdichroic film which reflects the R light and transmits the G lighttherethrough is formed on a first opposed surface obtained by bondingthe first prism 90 a and the second prism 90 b, and a second dichroicfilm which transmits the R light and the G light therethrough andreflects the B light is formed on a second opposed surface obtained bybonding the first prism 90 a and the third prism 90 c.

Therefore, in this three-color combination prism 90, the R light whichhas entered from the first prism 90 a is reflected by the first dichroicfilm, transmitted through the second dichroic film and enters the thirdprism 90 c. Moreover, the G light which has entered from the secondprism 90 b is transmitted through the first and second dichroic films asit is and enters the third prism 90 c. Additionally, the B light whichhas entered from the third prism 90 c is reflected by the seconddichroic film. The respective image lights of the R light, the G lightand the B light are subjected to color combination in this third prism90 c, and color-combined image light obtained by the three-colorcombination prism 90 enters the projection lens 92 through a ¼ waveplate 91, and is magnified and projected onto a non-illustrated screenby this projection lens 92 to form an actual image, thereby displayingthe color-combined image light.

As described above, since this projection type display apparatus 50 ofEmbodiment 2 also has a configuration in which the optical elementsconstituting the color separation optical system, the polarization spit,the spatial light modulation, the color combination optical systemportion and the projection lens are arranged on the same plane, theentire apparatus can be constituted on the same plane, whereby a heightof the apparatus can be reduced to obtain the compact apparatus.Further, since the optical path lengths from the light source 51 to thereflective liquid crystal panels 83 for the respective color lights areequal to each other, a relay lens is not necessary in the colorseparation optical system, and hence the configuration of the opticalsystem can be simplified, thereby facilitating manufacture and reducinga cost.

Furthermore, in Embodiment 2, as shown in FIG. 28, when the G lightenters the reflective liquid crystal panel assembly 80G for the G lightin a state where the second prism 90 b of the three-color combinationprism 90 faces, e.g., the reflective liquid crystal panel assembly 80Gfor the G light with a gap therebetween on the upper surface 70 a of thebase board 70, temperatures of the reflective polarizing plate 82, thereflective liquid crystal panel 83 and the transmission type polarizingplate 84 attached and arranged on the triangular prismatic housing 81for the G light whose inside is sealed and the second prism 90 b in thethree-color combination prism 90 are increased due to the light from thelight source 51. Therefore, in order to avoid an increase intemperatures of these optical members, a fan 71 as air-cooling means isrotatably set on the lower surface 70 b side of the base board 70.

Based on this configuration, a first fan hole 70 c is formed through thebase board 70 in accordance with a gap between the reflective liquidcrystal panel assembly 80G for the G light and the second prism 90 b inthe three-color combination prism 90, and a second fan hole 70 d isformed through the same to face the heat sink 83 b attached on the rearsurface of the reflective liquid crystal panel 83 for the G light.

Furthermore, an air stream W generated when rotating the fan 71 issupplied to the upper surface 70 a side of the base board 70 from thelower surface 70 b side of the base board 70 through the first andsecond fan holes 70 c and 70 d formed through this base board 70. Inthis example, the air stream W which has passed through the first fanhole 70 c is supplied to the gap formed between the transmission typepolarizing plate 84 attached on the triangular prismatic housing 81 forthe G light and the incidence surface of the second prism 90 b of thethree-color combination prism 90 to cool the surface of the transmissiontype polarizing plate 84 for the G light and the incidence surface ofthe second prism 90 b in the three-color combination prism 90. Moreover,the air stream W which has passed through the second fan hole 70 d coolsthe heat sink 83 b attached on the rear surface of the reflective liquidcrystal panel 83 for the G light. Therefore, it is possible to suppressan increase in temperatures of the reflective liquid crystal panel 83for the G light, the transmission type polarizing plate 84 for the Glight and the three-color combination prism 90 to avoid deteriorationdue to heat generation. As a result, high luminance and high contrastcan be achieved, which contributes to an improvement in reliability withrespect to the projection type display apparatus 50 of Embodiment 2.

It is to be noted that, although not shown, the reflective liquidcrystal panel assembly 80R for the R light and the reflective liquidcrystal panel assembly 80B for the B light are also cooled by the fan 71provided on the lower surface 70 b side of the base board 70 like thereflective liquid crystal panel assembly 80G for the G light.

Additionally, it is apparent that each modification of Embodiment 2 canbe configured by adopting substantially the same configuration asModifications 1 to 9 of Embodiment 1 with respect to the projection typedisplay apparatus 50 of Embodiment 2 according to the present invention.Further, in modifications of this Embodiment 2, an absorption typepolarizing plate may be used for the R light as unnecessary polarizedlight removing means for each color light, and a reflective polarizingplate may be used for the G and B lights.

Embodiment 3

FIG. 29 is a perspective view showing a configuration of a projectiontype display apparatus of Embodiment 3 according to the presentinvention. FIG. 30 is a plan view showing a configuration of theprojection type display apparatus of Embodiment 3 according to thepresent invention. FIGS. 31A and 31B are a perspective view showingrespective reflective liquid crystal panel assemblies for R, G and Blights and a three-color combination cross dichroic prism and an X-Xcross-sectional view showing the reflective liquid crystal panelassembly for the R light, the three-color combination cross dichroicprism and the reflective liquid crystal panel assembly for the B lightin the projection display apparatus of Embodiment 3.

As shown in FIGS. 29 and 30, although a projection type displayapparatus 100 of Embodiment 3 according to the present invention isconstituted as a reflective type which reflects light as spatial lightmodulation elements corresponding to R light, G light and B light, it isdifferent from Embodiment 1 and Embodiment 2 in a configuration of anoptical system.

That is, as different from Embodiments 1 and 2, the projection typedisplay apparatus 100 of Embodiment 3 has an optical system comprisingtwo layers in a vertical direction. In this example, a light source 101which emits white light as non-polarized light and color separationoptical systems 108 and 112 which subjects the white light from thelight source 101 to color separation to obtain the R light, the G lightand the B light are arranged in an upper layer part of the opticalsystem and, on the other hand, respective reflective spatial lightmodulations elements (which will be referred to as reflective liquidcrystal panels hereinafter) 133 for the R, G and B lights, a three-colorcombination cross dichroic prism 140 which subjects image lights of therespective colors deflected and modulated in the respective liquidcrystal panels 133 for the R, G and B lights to color combination and aprojection lens 142 which projects color-combined image light obtainedin this three-color combination cross dichroic prism 140 are arranged ina lower layer part of the optical system.

First, the light source 101 emits the white light including the R light,the G light and the B light by using a metal halide lamp, a xenon lamp,a halogen lamp or the like. When the white light emitted from this lightsource 101 is reflected by a concave spherical reflecting mirror 102, itis turned to substantially parallel light to sequentially enter a firstfly-eye lens array 103 provided in front of the concave sphericalreflecting mirror 102 and a second fly-eye lens array 104 provided infront of this first fly-eye lens array 103. These first and secondfly-eye lens arrays 103 and 104 form a pair to constitute an integratorwhich homogenizes an illumination distribution in a light beam of thewhite light. It is to be noted that a non-illustrated visible externallight removing filter which cuts ultraviolet light and infrared lightmay be arranged in front of the light source 101.

Thereafter, the white light as the non-polarized light whoseillumination distribution has been homogenized by the first and secondfly-eye lens arrays 103 and 104 enters a polarization converting prismarray 105 as a polarization converting optical element. Thispolarization converting prism array 105 has the same configuration asthat of the polarization converting prism array 15 (FIG. 4) ofEmbodiment 1, includes a polarization split prism array and a λ/2 waveplate, and is entirely formed into a tabular shape. Further, the lighttransmitted through the polarization converting prism array 105 isturned to polarized light in a predetermined direction. In thisEmbodiment 3, the polarized light in a predetermined direction obtainedby the polarization converting prism array 105 is, e.g., P polarizedlight like Embodiment 1, but the present invention is not restrictedthereto, and it is possible to adopt a method which subjects the whitelight from the light source 101 to polarization conversion to obtain Spolarized light in the light converting prism array 105.

Then, the white light as the P polarized light transmitted through thepolarization converting prism array 105 is reflected by a first coldmirror 107 through a first field lens 106 so that its optical path isdeflected, and enters a first dichroic mirror 108. This first dichroicmirror 108 transmits component lights of two colors out of three primarycolor lights therethrough and reflects the remaining light. InEmbodiment 3, the first dichroic mirror 108 transmits the R lighttherethrough and reflects the G light and the B light, for example.

Furthermore, the R light transmitted through the first dichroic mirror108 is reflected by a second cold mirror 109 and condensed through asecond field lens 110. This R light is reflected by a second steeringmirror 111 for optical path direction conversion so that its opticalpath is deflected 90° toward the lower layer part. The R light reflectedby the first steering mirror 111 enters the reflective liquid crystalpanel assembly 130R for the R light arranged in the lower layer part.

On the other hand, the G light and the B light reflected by the firstdichroic mirror 108 enter a second dichroic mirror 112. This seconddichroic mirror 112 transmits the B light therethrough and reflects theG light, for example.

Then, when the G light reflected by the second dichroic mirror 112 isreflected by a second steering mirror 114 for optical path directionconversion through a third field lens 113, its optical path is deflected90° toward the lower layer part. The G light reflected by the secondsteering mirror 114 enters the reflective liquid crystal panel assembly130G for the G light arranged in the lower layer part.

On the other hand, the B light transmitted through the second dichroicmirror 112 is reflected by a third cold mirror 116 through a first relaylens 115, and condensed through a second relay lens 117. This B light isfurther reflected by a fourth cold mirror 118 and further reflected by athird steering mirror 120 for optical path direction conversion througha fourth field lens 119, and its optical path is thereby deflected 90°toward the lower layer part. The B light reflected by the third steeringmirror 120 enters the reflective liquid crystal panel assembly 130B forthe B light arranged in the lower layer part.

The first and second dichroic mirrors 108 and 112 constitute colorseparation optical systems which subject the white light from the lightsource 101 to color separation to obtain the R light, the G light andthe B light, and respective constituent members from the light source101 to the color separation optical systems 108 and 112 are respectivecolor light illuminating means for illuminating the reflective liquidcrystal panels (reflective spatial light modulation elements) 133 forthe respective color lights with the R light, the G light and the Blight.

Here, the reflective liquid crystal panel assembly 130R for the R light,the reflective liquid crystal panel assembly 130G for the G light andthe reflective liquid crystal panel assembly 130B for the B light allhave the same configuration, and each of the reflective liquid crystalpanel assembly 130R for the R light, the reflective liquid crystal panelassembly 130G for the G light and the reflective liquid crystal panelassembly 130B for the B light faces each of incidence surfaces 140 a to140 c of the three-color combination cross dichroic prism 140 as a colorcombination optical system formed into a rectangular parallelepipedshape with a gap therebetween.

In this example, the reflective liquid crystal panel assembly 130R forthe R light, the reflective liquid crystal panel assembly 130G for the Glight, the reflective liquid crystal panel assembly 130B for the B lightand the three-color combination cross dichroic prism 140 are fixed on anupper surface 121 a of a base board 121 formed of an aluminum materialor the like by an adhesive as shown in FIGS. 31A and 31B.

Additionally, as shown in FIGS. 29, 30, 31A and 31B, each of thereflective liquid crystal panel assembly 130R for the R light, thereflective liquid crystal panel assembly 130G for the G light and thereflective liquid crystal panel assembly 130B for the B light has thefollowing configuration. That is, a hollow triangular prismatic housing131 is prepared for each color light and, in the triangular prismatichousing 131 for each color light, a tabular reflective polarizing plate(a so-called “wire grid polarizer”) 132 as polarization splitting meansis attached on a first surface having an inclination angle ofapproximately 45° with respect to an optical axis of each color lightfrom each color light illuminating means from the light source 101 tothe color separation optical systems 108 and 112, and a reflectiveliquid crystal panel 133 is attached on a second surface orthogonal tothe optical axis of each color light transmitted through the reflectivepolarizing plate 132 for each color light. Further, a transmission typepolarizing plate 134 as unnecessary polarized light removing means isattached on a third surface orthogonal to the optical axis of each colorlight obtained by reflecting reflected light from the reflective liquidcrystal panel 133 for each color light by the reflective polarizingplate 132 for each color light. Furthermore, in a state where a spacesurrounded by the first to third surfaces of the triangular prismatichousing 131 is sealed from dust or the like by a lower surface and anupper surface, each side on which the transmission type polarizing plate134 for each color light is arranged faces each of the incidencesurfaces 140 a to 140 c of the three-color combination cross dichroicprism 140 with a gap therebetween.

In this example, in the triangular prismatic housing 131 for each colorlight, the reflective polarizing plate 132 is inclined approximately 45°with respect to the upper surface 121 a of the base board 121, and thetransmission type polarizing plate 134 is vertically provided withrespect to the upper surface 121 a of the base board 121.

Moreover, as different from Embodiments 1 and 2, on the reflectiveliquid crystal panel 133 for each color light is attached a wave plate133 a which is attached on the lower surface 121 b side of the baseboard 121, faces an opening portion 121 c formed through the base board121 and covers this opening portion 121 c from the upper side to correctthe liquid crystal corresponding to a pre-tilt by reciprocation.Additionally, a heat sink 133 b which cools the reflective liquidcrystal panel 133 is attached on a rear surface of the reflective liquidcrystal panel 133. It is to be noted that the description has been givenas to the example where the reflective liquid crystal panel 133 isattached on the lower surface 122 b side of the base board 121 inEmbodiment 3, but it can be attached on the upper surface 121 a side ofthe base board 121. In this case, it is good enough to form a fan hole,which cools the heat sink 133 b attached on the rear surface of thereflective liquid crystal panel 133, through the base board 121.

Further, when the R light, the G light and the B light of the Ppolarized components respectively enter the reflective liquid crystalpanel assembly 130R for the R light, the reflective liquid crystal panelassembly 130G for the G light and the reflective liquid crystal panelassembly 130B for the B light, the P polarized components alone aretransmitted through the reflective polarizing plate 132 for each colorlight attached on the triangular prismatic housing 131 for each colorlight to enter the reflective liquid crystal panel 133 for each colorlight.

Then, each light beam light-modulated and reflected in the reflectiveliquid crystal panel 133 for each color light in accordance with animage signal of each color of the R light, the G light or the B lightreturns to the corresponding reflective polarizing plate 132 for eachcolor light. Here, the light beam light-modulated and reflected by thereflective liquid crystal panel 133 for each color light is subject topolarization split by the reflective polarizing plate 132 for each colorlight, and each light beam whose linear polarized component (an Spolarized component in this example) in the other direction alone isreflected is transmitted through the transmission type polarizing plate134 for each color light, and then enters the three-color combinationcross dichroic prism 140 from each of the incidence surfaces 140 a to140 c thereof. It is to be noted that the three-color combination crossdichroic prism 140 is used as the color combination optical system inthis Embodiment 3, but such a “Phillips type prism” as described inconjunction with Embodiment 2 can be also used.

Subsequently, the image lights having the respective colors of the Rlight, the G light and the B light which have entered from therespective incidence surfaces 140 a to 140 c of the three-colorcombination cross dichroic prism 140 are subjected to color combinationby first and second dichroic films 140 e and 140 f formed in thethree-color combination cross dichroic prism 140, color-combined imagelight obtained by this three-color combination cross dichroic prism 140is emitted from an emission surface 140 d to enter a projection lens 142through the ¼ wave plate 141, and this light is magnified and projectedonto a non-illustrated screen by this projection lens 142 to form anactual image, thereby displaying the color-combined image light.

In this projection type display apparatus 100, as described above, sincethe color separation optical system and the color combination opticalsystem form the two layers in the vertical direction, an optical path isdrawn on an outer peripheral side to perform color separation in theupper layer part, and a light beam is led to the polarization split, thespatial light modulation, the color combination optical system and theprojection lens in the lower layer part. Therefore, even if the entireoptical system is reduced in size, drawing the optical path does notinvolve a lot of trouble, and the arrangement of the optical elementshave leeway.

Here, in Embodiment 3, when the R light, the G light and the B lightrespectively enter the reflective liquid crystal panel assembly 130R forthe R light, the reflective liquid crystal panel assembly 130G for the Glight and the reflective liquid crystal panel assembly 130B for the Blight, temperatures of the reflective polarizing plate 132, thereflective liquid crystal panel 133 and the transmission type polarizingplate 134 attached and arranged on the triangular prismatic housing 131for each color light whose inside is sealed and the respective incidencesurfaces 140 a to 140 c of the three-color cross dichroic prism 140 areincreased due to the light from the light source 101. Therefore, inorder to avoid an increase in temperatures of these optical members, asshown in FIGS. 31A and 31B, a fan 122 as air-cooling means is rotatablyset on the lower surface 121 b side of the base board 121.

Based on this configuration, each fan hole 121 d is formed through thebase board 121 in accordance with each gap formed between the reflectiveliquid crystal panel assemblies 130R, 130G and 130B for the respectivecolor lights and the respective incidence surfaces 140 a to 140 c of thethree-color combination cross dichroic prism 140.

Further, an air stream W generated when rotating the fan 122 istransmitted to the upper surface 121 a side of the base board 121 fromthe lower surface 121 b side of the base board 121 through the fan hole121 d formed in this base board 121. Here, the air stream W which haspassed through the fan hole 121 d is supplied into each gap formedbetween the transmission type polarizing plate 134 attached on thetriangular prismatic housing 131 for each color light and each of theincidence surfaces 140 a to 140 c of the three-color combination crossdichroic prism 140 to cool a surface of the transmission type polarizingplate 134 for each color light and each of the incidence surfaces 140 ato 140 c of the three-color combination cross dichroic prism 140.Furthermore, the air stream W from the fan 122 cools the heat sink 133 battached on the rear surface of the reflective liquid crystal panel 133for each color light. Therefore, it is possible to suppress an increasein temperatures of the reflective liquid crystal panel 133 for eachcolor light, the transmission type polarizing plate 134 for each colorlight and the three-color combination cross dichroic prism 140 to avoiddeterioration due to heat generation, whereby high luminance and highcontrast can be achieved, which contributes to an improvement inreliability with respect to the projection type display apparatus 100 ofEmbodiment 3.

Moreover, it is apparent that each modification of Embodiment 3 can beconstituted by adopting substantially the same configuration asModifications 1 to 9 of Embodiment 1 with respect to the projection typedisplay apparatus 100 of Embodiment 3 according to the presentinvention. Additionally, in modifications of this Embodiment 3, anabsorption type polarizing plate may be used for the R light and areflective polarizing plate may be utilized for the G and B lights asunnecessary polarized light removing means for each color light.

It should be understood that many modifications and adaptations of theinvention will become apparent to those skilled in the art and it isintended to encompass such obvious modifications and changes in thescope of the claims appended hereto.

1-13. (canceled)
 14. A projection type display apparatus comprising: areflective spatial light modulation element for each color lightcorresponding to each of R light, G light and B light; each color lightilluminating means for illuminating the reflective spatial lightmodulation element for each color light with each of the R light, the Glight and the B light; a reflective polarizing plate for each colorlight which transmits a polarized component in one direction of each ofthe R light, the G light and the B light from each color lightilluminating means therethrough, and reflects as image light of eachcolor a polarized component in the other direction different from thepolarized light in one direction obtained by subjecting each of thetransmitted R light, G light and B light to light modulation inaccordance with an image signal of each color light by the reflectivespatial light modulation element for each color light; unnecessarypolarized light removing means for each color light for removing anunnecessary polarized component with respect to the image light of eachcolor from the reflective spatial light modulation element for eachcolor light reflected by the reflective polarizing plate for each colorto emit the image light of each color without the unnecessary polarizedcomponent; a color combination optical system which subjects the imagelight of each color emitted from the unnecessary polarized lightremoving means for each color light to color combination to emit thethus combined light as color-combined image light; and a projection lenswhich projects the color-combined image light, wherein the unnecessarypolarized light removing means for each color light is a polarizingplate which absorbs unnecessary polarized light with respect to the Rlight and the G light and, on the other hand, it is a polarizing platewhich reflects the unnecessary polarized light with respect to the Blight.
 15. The projection type display apparatus according to claim 14,further comprising air-cooling means for air-cooling the unnecessarypolarized light removing means for each color light.
 16. The projectiontype display apparatus according to claim 14, wherein a triangularprismatic housing for each color light is arranged in proximity to thecolor combination optical system, the triangular prismatic housing foreach color light having: a first surface which has an inclination angleof approximately 45° with respect to an optical axis of each color lightfrom each color light illuminating means and on which the reflectivepolarizing plate for each color light is attached; a second surfacewhich is orthogonal to the optical axis of each color light transmittedthrough the reflective polarizing plate for each color light and onwhich the reflective spatial light modulation element for each colorlight is attached; a third surface which is orthogonal to the opticalaxis of each color light obtained by reflecting reflected light from thereflective spatial light modulation element for each color light by thereflective polarizing plate for each color and on which the unnecessarypolarized light removing means for each color light is attached; and alower surface and an upper surface which seal a space surrounded by thefirst surface to the third surface.
 17. (canceled)
 18. The projectiontype display apparatus according to claim 17, wherein the transparentglass plate for each color light has a function of restricting a disusedwavelength band.
 19. (canceled)
 20. The projection type displayapparatus according to claim 19, wherein the transparent glass platesfor the R light and the G light have a function of restricting a disusedwavelength band. 21-25. (canceled)
 26. The projection type displayapparatus according to claim 14, wherein the unnecessary polarized lightremoving means for each color light has a function of restricting adisused wavelength band. 27-29. (canceled)